The list is comprised of open-source software organized in alphabetical order.
1) Audio / Music
2) Image / Video
3) Communication / News
4) Personal planning
5) Security
6) Knowledge Management / Document preparation
7) General
8) Scripts
9) Games
1) Audio / Music
Cmus - music player (alternative: Moc).
FFmpeg - tools for transcoding, streaming and playing of multimedia files.
FLAC - lossless audio coding format.
Pulsemixer - mixer for PulseAudio.
Ogg Vorbis - lossy audio coding format.
Opus - lossy audio coding format (preference: 128-160 VBR).
2) Image / Video
Webp - image format (replacement for JPEG, PNG, GIF).
3) Communication / News
Mutt Wizard - email client (alternative: Aerc).
Newsboat - rss/atom feed reader.
4) Personal planning
Calcurse - text-based calendar and todo manager (alternatives: Remind, Khal, When).
GNU Pem - personal expense manager (alternative: Ledger).
Taskwarrior - to-do manager (alternative: Task).
5) Security
Pass - password manager (alternative: Keepass XC).
Veracrypt - data encryption (alternative: Cryptomator).
6) Knowledge Management / Document preparation
BibTeX - lists of references (works well with LaTeX).
Groff - document preparation system (alternative: LaTeX).
Libreoffice - office productivity suite.
Mdp - markdown presentation tool.
Neovim - text editor (alternative: Nano).
NovelWritter - text editor for writing novels and larger projects.
Xapers - personal document indexing system, geared towards academic journal articles.
7) General
Bc - GNU bc arbitrary precision calculator language.
Cht.sh - cheat sheets repositories.
Cmatrix - screensaver (alternative: Asciiquarium).
Rofi - window switcher, application launcher and dmenu replacement.
8) Scripts
8) Games