Emacs on Debian12 config for several users

In several cases it is convenient to share the power of Emacs amongst several users on the same Debian12 host and this article provides a dense and terse overview how to manage this task in a sure&fire manner.

The file which executes by each instance of Emacs allocated at /etc/emacs/site-start.d/00debian.el So it is reasonable to put all common settings into it.

They are native for Debian and it might be secure to use them instead the third-part ELPA/MELPA. Of course all they are system-wide, and it is easy to include it in the user's config by (require 'package-name) operator.

apt-cache search elpa 2>&1

elpa-a - functions for dealing with associative structures
elpa-ace-link - selecting a link to jump to
elpa-ace-popup-menu - replace GUI popup menu with something more efficient
elpa-ace-window - selecting a window to switch to
elpa-acl2 - Computational Logic for Applicative Common Lisp: emacs interface
elpa-adaptive-wrap - smart line-wrapping with wrap-prefix
elpa-agda2-mode - dependently typed functional programming language — emacs mode
elpa-aggressive-indent - Emacs minor mode that reindents code after every change
elpa-apache-mode - Emacs major mode for editing Apache configuration files
elpa-apiwrap - api-wrapping macros
elpa-assess - test support functions for Emacs
elpa-atomic-chrome - edit a web-browser text entry area with Emacs
elpa-ats2-mode - ATS version 2 programming language emacs mode
auto-complete-el - transitional package for elpa-auto-complete
elpa-auto-complete - intelligent auto-completion extension for GNU Emacs
elpa-auto-dictionary - automatic dictionary switcher for Emacs spell checking
autodep8 - DEP-8 test control file generator
elpa-avy - jump to things in Emacs tree-style
elpa-avy-menu - library providing avy-powered popup menu
elpa-bar-cursor - switch Emacs block cursor to a bar
elpa-beacon - highlight the cursor whenever the window scrolls
elpa-beginend - redefine M-< and M-> for some modes to get to meaningful locations
elpa-bm - visual bookmarks for GNU Emacs
elpa-bongo - buffer-oriented media player for GNU Emacs
elpa-boxquote - quote text in Emacs with a semi-box
elpa-browse-kill-ring - interactively insert items from kill-ring
elpa-bui - Emacs Buffer interface library
c-sig - Transition package, c-sig to elpa-c-sig
elpa-c-sig - signature tool for GNU Emacs
elpa-caml - emacs mode for editing OCaml programs
ocaml-mode - transitional package to elpa-caml
elpa-ps-ccrypt - Emacs addon for working with files encrypted with ccrypt
elpa-char-menu - create your own menu for fast insertion of arbitrary symbols
elpa-circe - client for IRC in Emacs
elpa-citar - Act on bibliographic references from Emacs
elpa-closql - Store EIEIO objects using EmacSQL
elpa-clues-theme - cream/brown/orange color theme for Emacs
migemo-el - transitional dummy package: elpa-migemo
elpa-color-theme-modern - deftheme reimplementation of classic Emacs color-themes
elpa-company - Modular in-buffer completion framework for Emacs
elpa-compat - COMPATibility Library for Emacs
cl-consfigurator - Lisp declarative configuration management system
elpa-consult - Useful commands based on completing-read for Emacs
elpa-crdt - collaborative editing environment for Emacs
elpa-csv-mode - Emacs major mode for editing comma, char, and tab separated values
elpa-dap-mode - DAP UI controls implemented using treemacs.
darcsum - Transition package, darcsum to elpa-darcsum
elpa-darcsum - pcl-cvs like interface for managing darcs patches
elpa-dash - modern list manipulation library for Emacs
debian-el - Transition package, debian-el to elpa-debian-el
elpa-debian-el - Emacs helpers specific to Debian users
elpa-debpaste - paste.debian.net client for Emacs
elpa-deft - Emacs mode to browse, filter, and edit plain text notes
devscripts-el - Transition package, devscripts-el to elpa-devscripts
elpa-devscripts - Emacs wrappers for the commands in devscripts
dh-elpa - Debian helper tools for packaging emacs lisp extensions
dh-elpa-helper - helper package for emacs lisp extensions
dh-make-elpa - helper for creating Debian packages from ELPA packages
elpa-diff-hl - highlight uncommitted changes using VC
elpa-diffview - view diffs in side-by-side format
elpa-diminish - hiding or abbreviation of the mode line displays of minor-modes
elpa-dimmer - visually highlight the selected buffer
elpa-dired-du - dired with recursive directory sizes
elpa-dired-quick-sort - persistent quick sorting of dired buffers in various ways
elpa-dired-rsync - support for rsync from Emacs dired buffers
elpa-discover-my-major - discover key bindings and their meaning for the current Emacs major mode
elpa-dockerfile-mode - Major mode for editing Docker's Dockerfiles
dpkg-dev-el - Transition package, dpkg-dev-el to elpa-dpkg-dev-el
elpa-dpkg-dev-el - Emacs helpers specific to Debian development
elpa-dumb-jump - jump to definition for multiple languages without configuration
elpa-ebib - BibTeX database manager for Emacs
elpa-ediprolog - Emacs Does Interactive Prolog
elpa-editorconfig - coding style indenter for all editors - Emacsen plugin
elpa-eglot - Emacs client for Language Server Protocol servers
elpa-el-mock - tiny mock and stub framework for Emacs Lisp
elpa-el-x - Emacs Lisp extensions
elpa-elfeed - Emacs Atom/RSS feed reader
elpa-bug-hunter - automatically debug and bisect your init.el or .emacs file
elpa-elisp-refs - find callers of elisp functions or macros
elpa-elm-mode - Major Emacs mode for editing Elm source code
libelpa-dev - Eigenvalue SoLvers for Petaflop-Applications (Development version)
libelpa19 - Eigenvalue SoLvers for Petaflop-Applications
elpa-darkroom - remove visual distractions and focus on writing
elpa-ligature - display typographical ligatures in major modes
elpa-migemo - Japanese incremental search with Romaji on Emacsen
elpa-rust-mode - Major Emacs mode for editing Rust source code
elpa-snakemake - Run Snakemake workflows from Emacs
elpa-snakemake-mode - provides syntax highlighting for snakekmake files in emacs
elpa-subed - Emacs mode for editing subtitles while playing the corresponding video
elpa-transient - Emacs key and popup interface for complex keybindings
elpa-transient-doc - Emacs key and popup interface for complex keybindings - Docs
elpa-undo-tree - Emacs minor mode for handling undo history as tree
elpa-elpher - friendly gopher and gemini client
elpa-elscreen - Screen for Emacsen
elscreen - Transition package, elscreen to elpa-elscreen
elpa-anzu - show number of matches in mode-line while searching
elpa-async - simple library for asynchronous processing in Emacs
elpa-bash-completion - add programmable bash completion to Emacs shell-mode
elpa-bind-map - bind personal keymaps in multiple locations
elpa-buttercup - behaviour-driven testing for Emacs Lisp packages
elpa-cmake-mode - Emacs major mode for editing CMake sources
elpa-ctable - table component for Emacs Lisp
elpa-emacs-dashboard - extensible emacs startup screen showing you what's most important
elpa-db - database interface for Emacs Lisp
elpa-debase - D-Bus convenience layer for Emacs
elpa-concurrent - higher level library for concurrent tasks
elpa-deferred - simple asynchronous functions for Emacs Lisp
elpa-ednc - Emacs Desktop Notification Center
elpa-discomfort - UDisks2 UI for Emacs, to mount & unmount disks
elpa-doom-themes - opinionated pack of modern Emacs color-themes
elpa-epc - RPC stack for Emacs Lisp
elpa-vc-fossil - Emacs VC backend for the Fossil Version Control system
elpa-git-messenger - pop up last commit information of current line
elpa-git-modes - major modes for editing Git configuration files
elpa-gitattributes-mode - major mode for editing Git configuration files (gitattributes)
elpa-gitconfig-mode - major mode for editing Git configuration files (gitconfig and gitmodules)
elpa-gitignore-mode - major mode for editing Git configuration files (gitignore)
emacs-goodies-el - Miscellaneous add-ons for Emacs
elpa-haskell-tab-indent - tab-based indentation for haskell-mode
elpa-helm-ag - Silver Searcher integration with Emacs Helm
elpa-highlight-indentation - highlight the indentation level in Emacs buffers
elpa-htmlize - convert buffer text and decorations to HTML
elpa-counsel - collection of Ivy-enhanced versions of common Emacs commands
elpa-ivy - generic completion mechanism for Emacs
elpa-ivy-hydra - additional key bindings for Emacs Ivy
elpa-swiper - alternative to Emacs' isearch--with an overview
elpa-jabber - Jabber client for Emacsen
elpa-kv - key/value data structure functions for Emacs Lisp
elpa-vterm - fully-fledged terminal emulator inside GNU Emacs based on libvterm - elisp
elpa-lintian - Examine Lintian packaging hints in Emacs
elpa-lsp-haskell - Haskell support for lsp-mode
elpa-lsp-ui - UI modules for lsp-mode
elpa-memoize - memoization functions
elpa-neotree - directory tree sidebar for Emacs that is like NERDTree for Vim
elpa-noflet - Emacs Lisp noflet macro for dynamic, local advice
elpa-openwith - seamlessly open files in external programs with Emacs
elpa-orgalist - Manage Org-like lists in non-Org Emacs buffers
elpa-pass - major mode for password-store
elpa-pdf-tools - Display and interact with pdf in Emacs
elpa-pdf-tools-server - server for Emacs's pdf-tools
elpa-pg - Emacs Lisp interface for PostgreSQL
elpa-pod-mode - Emacs major mode for editing .pod files
elpa-posframe - Emacs library to Pop a frame at point
elpa-powerline - Emacs version of the Vim powerline
elpa-python-environment - virtualenv API for Emacs Lisp
elpa-request - Compatibility layer for URL request in Emacs
elpa-session - use variables, registers and buffer places across sessions
elpa-smeargle - highlight region by last updated time
elpa-svg-lib - SVG tags, progress bars & icons for Emacs
elpa-tablist - tablist adds maks and filters to tabulated-list-mode
elpa-uuid - UUID/GUID library for Emacs Lisp
elpa-simple-httpd - pure elisp HTTP server
elpa-websocket - Emacs WebSocket client and server
elpa-wgrep - edit multiple Emacs buffers using a master grep pattern buffer
elpa-wgrep-ack - edit multiple Emacs buffers using a master ack pattern buffer
elpa-wgrep-ag - edit multiple Emacs buffers using a master ag pattern buffer
elpa-wgrep-helm - edit multiple Emacs buffers with a helm-grep-mode buffer
elpa-which-key - display available keybindings in popup
elpa-world-time-mode - Emacs mode to compare timezones throughout the day
elpa-emacsql - high level SQL database frontend for Emacs (abstractions)
elpa-emacsql-mysql - high level SQL database frontend for Emacs (MySQL backend)
elpa-emacsql-psql - high level SQL database frontend for Emacs (PostgreSQL backend)
elpa-emacsql-sqlite - high level SQL database frontend for Emacs (SQLite backend)
elpa-emacsql-sqlite3 - Yet another EmacSQL backend for SQLite
elpa-embark - Emacs Mini-Buffer Actions Rooted in Keymaps
elpa-ement - Matrix client for Emacs
elpa-engine-mode - define and query search engines from within Emacs
elpa-epl - Emacs Package Library
elpa-eproject - assign files to Emacs projects, programmatically
elpa-ert-async - asynchronous tests for the Emacs ERT testing framework
elpa-ert-expectations - very simple unit test framework for Emacs Lisp
elpa-esh-help - add some help functions and support for Eshell
elpa-eshell-bookmark - integrate bookmarks with Eshell
elpa-eshell-git-prompt - Eshell prompt themes for Git users
elpa-eshell-prompt-extras - display extra information in your Eshell prompt
elpa-eshell-up - quickly go to a specific parent directory in eshell
elpa-eshell-z - cd to frequent directory in eshell
elpa-ess - Emacs mode for statistical programming and data analysis
elpa-esup - Emacs StartUp Profiler
elpa-esxml - XML, ESXML and SXML library for Emacs Lisp
elpa-evil - extensible vi layer for Emacs
elpa-evil-paredit - emacs extension, integrating evil and paredit
elpa-exec-path-from-shell - get environment variables such as $PATH from the shell
elpa-expand-region - Increase selected region in Emacs by semantic units
expand-region-el - Transition package, expand-region-el to elpa-expand-region
elpa-exwm - full-featured tiling X window manager for Emacs
elpa-exwm-mff - mouse-follows-focus for EXWM
elpa-eyebrowse - simple-minded way of managing window configs in Emacs
elpa-f - modern API for working with files and directories in Emacs Lisp
elpa-faceup - Regression test system for font-lock
elpa-fill-column-indicator - graphically indicate the fill column
elpa-find-file-in-project - quick access to project files in Emacs
elpa-flx - sorting algorithm for fuzzy matching in Emacs
elpa-flx-ido - allows Emacs Ido to use the flx sorting algorithm
elpa-flycheck - modern on-the-fly syntax checking for Emacs
elpa-flycheck-package - flycheck checker for Elisp package authors
elpa-folding - folding-editor minor mode for Emacs
fortran-language-server - Fortran Language Server for the Language Server Protocol
elpa-fountain-mode - Emacs major mode for screenwriting in Fountain markup
elpa-fricas - General purpose computer algebra system: emacs support
elpa-fsm - state machine library
elpa-geiser - enhanced Scheme interaction mode for Emacs
geiser - Transition Package, geiser to elpa-geiser
elpa-ggtags - improved Emacs interface to GNU GLOBAL
elpa-ghub - minuscule client for the Github API
elpa-ghub+ - thick GitHub API client built on ghub
elpa-git-annex - Emacs integration for git-annex
elpa-git-auto-commit-mode - Emacs Minor mode to automatically commit and push with git
elpa-git-timemachine - walk through git revisions of a file
elpa-gitlab-ci-mode - Emacs mode for editing GitLab CI files
elpa-gnuplot-mode - Gnuplot mode for Emacs
gnuplot-mode - Transition Package, gnuplot-mode to elpa-gnuplot-mode
elpa-go-mode - Emacs mode for editing Go code
golang-mode - Emacs mode for editing Go code -- transitional package
elpa-golden-ratio - automatic resizing of Emacs windows to the golden ratio
elpa-goo - generic object-orientator (Emacs support)
elpa-goto-chg - navigate the point to the most recent edit in the buffer
elpa-graphql - GraphQL utilities
elpa-graphviz-dot-mode - Emacs mode for the dot-language used by graphviz.
elpa-haskell-mode - major mode for editing Haskell in Emacs
elpa-helm - Emacs incremental completion and selection narrowing framework
elpa-helm-core - Emacs Helm library files
elpa-helm-org - Emacs Helm for Org-mode headlines and keywords completion
elpa-helm-projectile - Helm integration for Projectile
elpa-helpful - better *help* buffer
elpa-highlight-numbers - highlight numbers in source code
elpa-hl-todo - highlight TODO and similar keywords in comments and strings
howm - Note-taking tool on Emacs
elpa-ht - hash table library for Emacs
elpa-hungry-delete - enable hungry deletion in all modes
elpa-hydra - make Emacs bindings that stick around
elpa-lv - other echo area
elpa-ibuffer-projectile - group buffers in ibuffer list by Projectile project
elpa-ibuffer-vc - group ibuffer list by VC project and show VC status
elpa-ido-completing-read+ - completing-read-function using ido
elpa-ido-vertical-mode - make ido-mode display vertically
elpa-iedit - edit multiple regions in the same way simultaneously
elpa-imenu-list - show the current Emacs buffer's imenu entries in a separate window
elpa-inform-mode - Emacs major mode for editing Inform 6 source
inform-mode - transitional dummy package
elpa-initsplit - code to split customizations into different files
elpa-irony - Emacs C/C++ minor mode powered by libclang
elpa-jinja2-mode - Emacs major mode for editing jinja2 code
elpa-js2-mode - Emacs mode for editing Javascript programs
elpa-key-chord - map pairs of simultaneously pressed keys to commands
elpa-kotlin-mode - Emacs major mode for kotlin
elpa-lbdb - Little Brother's DataBase Emacs extensions
elpa-ledger - command-line double-entry accounting program (emacs interface)
elpa-let-alist - let-bind values of an assoc-list by their names in Emacs Lisp
elpa-linum-relative - display relative line number in Emacs
elpa-load-relative - relative file load (within a multi-file Emacs package)
elpa-loop - friendly imperative loop structures for Emacs Lisp
elpa-lsp-java - Java LSP support for emacs
elpa-lsp-mode - Emacs client/library for the Language Server Protocol
elpa-lsp-treemacs - treemacs integration for Emacs LSP
elpa-lua-mode - Emacs major-mode for editing Lua programs
elpa-m-buffer - list-oriented, functional buffer manipulation
elpa-macaulay2 - Software system for algebraic geometry research (Emacs package)
elpa-git-commit - Major mode for editing git commit message
elpa-magit - Emacs interface for Git
elpa-magit-section - Collapsible sections like in Magit
elpa-magit-annex - git-annex subcommands for magit
elpa-magit-forge - Work with Git forges from the comfort of Magit
elpa-magit-popup - Use popup like Magit
elpa-magit-todos - show source file TODOs in Magit
elpa-mailscripts - Emacs utilities for handling mail on Unixes
elpa-makey - flexible context menu system
elpa-marginalia - Marginalia in the Emacs minibuffer
elpa-markdown-mode - mode for editing Markdown-formatted text files in GNU Emacs
elpa-markdown-toc - Emacs TOC (table of contents) generator for markdown files
elpa-mastodon - Emacs client for the Mastodon and Pleroma social networks
elpa-meson-mode - Major mode for the Meson build system files
elpa-message-templ - templates for Emacs message-mode
elpa-minimap - sidebar showing a "mini-map" of a buffer
elpa-mocker - mocking framework for Emacs
elpa-modus-themes - set of accessible themes conforming with WCAG AAA accessibility standard
elpa-monokai-theme - fruity color theme for Emacs
elpa-move-text - move current line or region up and down
elpa-mpv - control a mpv via its IPC interface from Emacs
elpa-muse - author and publish projects using Wiki-like markup
elpa-mutt-alias - Emacs package to lookup and insert expanded Mutt mail aliases
elpa-muttrc-mode - Emacs major mode for editing muttrc
elpa-nginx-mode - major mode for editing nginx config files
elpa-no-littering - help keeping ~/.emacs.d clean
elpa-nose - easy Python test running in Emacs
elpa-notmuch - thread-based email index, search and tagging (emacs interface)
elpa-nov - featureful EPUB (ebook) reader mode for Emacs
elpa-ol-notmuch - Links to notmuch messages
elpa-olivetti - Emacs minor mode to more comfortably read and write long-lined prose
elpa-orderless - Emacs completion style that matches multiple regexps in any order
elpa-org-appear - auto-toggle visibility of org mode elements
elpa-org-bullets - show bullets in Org-mode as UTF-8 characters
elpa-org-contrib - additional Emacs Lisp libraries for Org-mode
elpa-org-d20 - Emacs minor mode for d20 tabletop roleplaying games
elpa-org-drill - emacs org-mode contrib for self-testing using spaced repetition
elpa-org-make-toc - Automatic tables of contents for Org files
elpa-org - Keep notes, maintain ToDo lists, and do project planning in emacs
org-mode - Transition Package, org-mode to elpa-org
elpa-org-present - minimalist presentation tool for Emacs org-mode
elpa-org-roam - non-hierarchical note-taking with Emacs Org-mode
elpa-org-tree-slide - presentation tool for org-mode
elpa-ox-texinfo+ - Extensions for Org's Texinfo exporter
elpa-package-lint - linting library for Elisp package authors
elpa-package-lint-flymake - package-lint Flymake backend
elpa-page-break-lines - Emacs mode to display ugly ^L page breaks as tidy horizontal lines
elpa-paredit - Emacs minor mode for structurally editing Lisp code
elpa-paredit-everywhere - cut-down version of paredit for non-lisp buffers
elpa-parent-mode - get major mode's parent modes
elpa-parsebib - Emacs Lisp library for parsing .bib files
elpa-password-store - Emacs support for the lightweight directory-based password manager
elpa-pcre2el - Emacs mode to convert between PCRE, Emacs and rx regexp syntax
elpa-persist - persist variables between Emacs Sessions
elpa-perspective - tagged workspaces in Emacs
elpa-pfuture - set of functions wrapping Emacs' process creation capabilities
elpa-php-mode - PHP Mode for GNU Emacs
elpa-pip-requirements - major mode for editing pip requirements files
elpa-pkg-info - provide information about Emacs packages
elpa-plz - HTTP library for Emacs
elpa-pointback - restore window points when returning to buffers
elpa-poke - Extensible editor for structured binary data (Emacs mode)
elpa-popup - visual popup user interface library for Emacs
elpa-pos-tip - Show tooltip at point
elpa-project - Emacs library for operations on the current project
elpa-projectile - project interaction library for Emacs
elpa-protobuf-mode - Emacs addon for editing protocol buffers
elpa-puppet-mode - Emacs major mode for Puppet manifests
elpa-py-autopep8 - use autopep8 to beautify a Python buffer
elpa-py-isort - use isort to sort the imports in a Python buffer
elpa-pyim-basedict - default pinyin dict for pyim
elpa-pyim - Chinese input method support quanpin, shuangpin, wubi, cangjie and rime
elpa-pyvenv - Python virtual environment interface
elpa-qml-mode - Emacs major mode for editing QT Declarative (QML) code
elpa-queue - queue data structure for Emacs Lisp
elpa-racket-mode - emacs support for editing and running racket code
elpa-rainbow-delimiters - Emacs mode to colour-code delimiters according to their depth
elpa-rainbow-identifiers - highlight identifiers according to their names
elpa-rainbow-mode - colorize color names in buffers
elpa-recursive-narrow - narrow-to-region that operates recursively
elpa-redtick - tiny pomodoro timer for Emacs
elpa-relint - Emacs Lisp regexp mistake finder
elpa-restart-emacs - restart emacs from within emacs
elpa-rich-minority - clean-up and beautify the list of minor-modes in Emacs' mode-line
elpa-ac-rtags - auto-complete back-end for RTags
elpa-company-rtags - company back-end for RTags
elpa-flycheck-rtags - flycheck integration for RTags
elpa-helm-rtags - helm interface for RTags
elpa-ivy-rtags - ivy back-end for RTags
elpa-rtags - emacs front-end for RTags
elpa-s - string manipulation library for Emacs
elpa-scala-mode - Emacs major mode for editing scala source code
scala-mode-el - transitional dummy package, scala-mode-el to elpa-scala-mode
elpa-seq - sequence manipulation functions for Emacs Lisp
elpa-sesman - session manager for Emacs IDEs
elpa-shut-up - Emacs Lisp macros to quieten Emacs
elpa-ag - Emacs frontend to ag
silversearcher-ag-el - transitional dummy package, silversearcher-ag-el to elpa-ag
elpa-smart-mode-line - powerful and beautiful mode-line for Emacs
elpa-smart-mode-line-powerline-theme - Smart Mode Line themes that use Emacs Powerline
elpa-smex - M-x interface for Emacs with Ido-style fuzzy matching
elpa-sml-mode - Emacs major mode for editing Standard ML programs
sml-mode - Transition package, sml-mode to elpa-sml-mode
elpa-solarized-theme - port of Solarized theme to Emacs
elpa-spinner - spinner for the Emacs modeline for operations in progress
elpa-srv - RFC2782 (SRV record) client for emacs
elpa-suggest - discover Emacs Lisp functions based on examples
elpa-super-save - auto-save buffers, based on your activity
elpa-sxiv - run the sxiv image viewer
elpa-system-packages - functions to manage system packages
elpa-systemd - major mode for editing systemd units
elpa-tabbar - Emacs minor mode that displays a tab bar at the top
elpa-taxy - Emacs programmable taxonomical grouping for arbitrary objects
elpa-taxy-magit-section - View Emacs Taxy structs in a Magit Section buffer
elpa-transmission - Emacs interface to a Transmission session
elpa-treemacs - tree layout file explorer for Emacs
elpa-treemacs-evil - tree layout file explorer for Emacs
elpa-treemacs-magit - tree layout file explorer for Emacs
elpa-treemacs-projectile - tree layout file explorer for Emacs
elpa-treepy - Generic tree traversal tools
elpa-tuareg - emacs-mode for OCaml programs
tuareg-mode - transitional package, tuareg-mode to elpa-tuareg
elpa-undercover - test coverage library for Emacs Lisp
elpa-bind-chord - key-chord binding helper for use-package-chords
elpa-bind-key - simple way to manage personal keybindings
elpa-use-package - configuration macro for simplifying your .emacs
elpa-use-package-chords - key-chord keyword for use-package
elpa-use-package-ensure-system-package - autoinstall system packages
elpa-vala-mode - Emacs editor major mode for vala source code
vala-mode-el - Transition Package, vala-mode-el to elpa-vala-mode
elpa-verbiste - French and Italian conjugator - emacs extension
verbiste-el - transitional package, verbiste-el to elpa-verbiste
elpa-vertico - Performant and minimalistic vertical completion UI for Emacs
elpa-vimish-fold - fold text in GNU Emacs like in Vim
elpa-helm-virtualenvwrapper - helm-source for virtualenvwrapper.el
elpa-virtualenvwrapper - featureful virtualenv tool for Emacs
elpa-visual-fill-column - Emacs mode that wraps visual-line-mode buffers at fill-column
elpa-visual-regexp - in-buffer visual feedback while using Emacs regexps
elpa-volume - tweak your sound card volume from Emacs
elpa-wc-mode - display a word count in the Emacs modeline
elpa-web-mode - major emacs mode for editing web templates
elpa-weechat - Chat via WeeChat's relay protocol in Emacs.
elpa-with-editor - call program using Emacs as $EDITOR
elpa-with-simulated-input - macro to simulate user input non-interactively
elpa-writegood-mode - Emacs minor mode that provides hints for common English writing problems
elpa-writeroom-mode - distraction-free writing for Emacs
elpa-ws-butler - unobtrusively remove trailing whitespace in Emacs
elpa-xcite - exciting cite utility for Emacsen
xcite - Transition Package, xcite to elpa-xcite
elpa-xcscope - Interactively examine a C program source in emacs
xcscope-el - Transition Package, xcscope-el to elpa-xcscope
elpa-xelb - pure Elisp implementation of X11 protocol
elpa-xml-rpc - Emacs Lisp XML-RPC client
elpa-xr - convert string regexp to rx notation
elpa-xref - Library for cross-referencing commands in Emacs
elpa-yaml - YAML parser and encoder for Elisp
elpa-yaml-mode - Emacs major mode for YAML files
elpa-yasnippet - template system for Emacs
yasnippet - transition Package, yasnippet to elpa-yasnippet
elpa-yasnippet-snippets - Andrea Crotti's official YASnippet snippets
youtube-dl - download videos from YouTube and other sites (transitional package)
yt-dlp - downloader of videos from YouTube and other sites
elpa-zenburn-theme - low contrast color theme for Emacs
elpa-ztree - text mode directory tree
elpa-zzz-to-char - fancy version of `zap-to-char' command

By default all they are installed into /usr/share/emacs/site-lisp/elpa

There are a plethora packages, provided by third-parties and not included into the official Debian release. They can be allocated in any folder in load-path, for this particular case in /usr/local/share/emacs/site-lisp:

ls /usr/local/share/emacs/site-lisp 2>&1

bookmark-plus
custom
elpy
ereader
google-translate
key-chord-0.7
kv-0.0.5
linkmarks
mw-thesaurus
nov.el
org-bullets-0.2.4
org-drill-2.7.0
powerthesaurus-0.4.0
speed-type-1.3
voca-builder-0.2.0

All them are in the default Emacs' load-path and accesible for each user, but it's necessary to add every package's folder into the pesonal load path. It might be defined manually, folder by folder, but here is the hack how to add all folders to load-path at once:

;; add all subdirs from the host's =site-lisp= to ~load-path~
(let* ((my-lisp-dir "/usr/local/share/emacs/site-lisp/")
       (default-directory my-lisp-dir)
       (orig-load-path load-path))
  (setq load-path (cons my-lisp-dir nil))
  (normal-top-level-add-subdirs-to-load-path)
  (nconc load-path orig-load-path))

NOTE load-path modificates only at Emacs initiation, so you're need to restart your favourite editor.

In several cases it is reasonable to put a large hunk of some configuration into a separate fine and include it into main user's config ~/.emacs in a single string:

(load "/usr/local/share/emacs/site-lisp/custom/<name_of_conf_hunk.el>")