Some of mine are grayjay, kotatsu, expenses, voyager, feeder, mull and syncthing
All of the above managed through Obtainium, directly from the source.
- Bitwarden (Google Play link)
- Eternity for Lemmy (Google Play link)
- HordeNG (taken down from Google play, but if was basically just a wrapper for a web app which you can install easily from the browser anyway - https://horde-ng.org)
- Baby Journal (also a web app wrapper, available as a web app at https://baby-journal.app)
- probably others from Google Play I don’t use that often and don’t remember whether they are open source or not
Three of those are made by me, but I also use them often (that’s why I created them in the first place).