Can share some of my favourites
- KISS laucher
- Floris Board (keyboard, which I love to use)
- Bitwarden + Aegis (password manager + OTP)
- Eternity (for browsing lemmy)
- Mull (hardened firefox fork)
- Organic maps (maps + directions)
- Track & Graph (for tracking trends/habits)
- WebApps (running sandboxed websites)
Just begun exploring using:
- Immich (selfhosted photos solution)
- ReThink (local dns/firewall tracking blocker)
Btw, I believe Obsidian isn’t FOSS.
I am not sure how well they stack up against the competition, as I haven’t really used them, but maybe they can hit the sweet-spot:
KDE has an office suite: Calligra. Windows and macOS support seems to be preliminary, what that means in terms of stability/performance, I don’t know.
As you also mention Figma working decently for you, you could take a look at Penpot.
In regards to your latex situation, maybe klatexformula, could be something for you. It generates images from latex. I’ve been pretty happy with it, in tandem with word processors, before fully jumping to latex. It’s pretty lightweight, their site does mention it needs a minimal version of latex though, which I don’t recall installing when using it, but both texlive, and miktex seem fairly small.
Edit: as others also mention OnlyOffice might also be an option for you.