I think it’s still alive, at least GmsCore had a new release last week

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.

I think it’s an interesting project. However I am not a fan of their decision to omit forward secrecy, and have thus passed on using it. At least for now.

Haven’t tried it but, DivestOS might also be an option.