https://www.passwordstore.org/
I sync this directory to my mobile device using megasync (linux packages and Android app available).
https://aur.archlinux.org/packages/megasync/
https://play.google.com/store/apps/details?id=mega.privacy.a...
Then I use `pass` on Android via the "Password Store" app (and the APG app to manage my PGP keys on mobile).
https://play.google.com/store/apps/details?id=com.zeapo.pwds...
The whole UX is super easy. Basically just PGP, plaintext files, and copy/paste.