

B2 -> B4
FOSS is the way.


B2 -> B4
I use Phocid, maybe a bit too minimalistic regarding you used Musicolet. It is only available on F-Droid though.
I bought a Fairphone 3 and put LineageOS on it a few years back and can recommend it. LineageOS is less secure than GrapheneOS as far as I can tell but the privacy aspect is there, as you have a completely degoogled phone. I have some friends that have the same setup on the newer Fairphones and they are also very happy and have a smoother experience than me, because it is a newer phone.
Fairphone is an European country that has a move to open source (https://www.fairphone.com/en/open-source/).
To the compatibility and functionality:
In general you will find an replacement for every app you now use that is from a big company. Open Source came a long way and most alternatives are even better in my opinion.
Mostly Neovim and Nano. Tried out ed in the UNIX4 tape that got recovered, was strange but fun to see where sed, grep and other commands got their name from.
GUI is still good old Sublime Text, but I almost completely switched to terminal based editors, I guess because of the nice work flow.