Late to the App Defaults train but here's what I use as of December 2023. For the latest list and Every Day Carry (EDC) list, see the Uses page.

• Operating System: NixOS (Desktop) / Android (Mobile)
• E-Mail: Thunderbird (Desktop) / Outlook (Mobile)
• Feed Reader: NewsBlur
• Podcasts: AntennaPod
• Music: Spotify
• Notes: Emacs (Org-Mode)
• Tasks: Emacs (Org-Mode) / Microsoft To-Do
• Office: LibreOffice
• Browser: Firefox
• Messaging: Element / Signal (Molly)
• Maps: OSMAnd~
• Text Editor: Visual Studio Code
• E-Book Management: Calibre
• Reading: Libby
• Video: mpv / VLC
• Authenticator: Aegis