Here's some excellent software I've come to love.

"Desktop" Linux

• KDE - Desktop environment - Very configurable and gets out of your way.
• Kate - Text editor - As with KDE, stays out of your way and edits text.
• PulseView - Waveform viewer - Plug in any hardware and view oscilloscope or logic analyzer output.
• KiCad - Schematic / PCBs
• Blender - 3D Modelling
• F3d - 3D viewer - Very basic but is great for instant viewing of 3D models
• KDE Connect - Phone companion - Closest thing to AirDrop plus more
• Okular - PDF viewer
• Ghostwriter - Markdown - Basic editor that stays out of your way, great for markdown

Android

• Auroura Store - App store - Allows downloading from Google Play without account or TOS
• Organic Maps - Map - Smooth OSM map app - fork of (?)
• OsmAnd - Map - Not as smooth but very powerful and configurable OSM maps
• StreetComplete - Map data editor
• Spectroid - Spectrum analyzer
• K-9 Mail - Mail client
• aCalandar - Calendar - Basically my favorite Android app. Extremely sane defaults, powerful yet intuitive event editing, excellent day and month views
• Florisboard - Keyboard - Still in alpha but could be a great Swiftkey alternative
• Podcast Addict - Podcasts - Very configurable pods with excellent automation ability
• Ruler - Calibrate it once and always have one with you.

All Around / Services

• Bitwarden - Password manager - Excellent polished software that works on anything.
• Joplin - Notes - Great desktop app, OK android app, markdown and seamless sync, no lock-in
• Signal - Messaging - Secure audited messaging app with everything I need and nothing I don't.
• Mullvad - VPN - No marketing at all, no affiliate program, externally audited security, simple billing, accepts cash
• VLC - Media player - Plays anything, FOSS, etc. etc.