Keepass/KeepssXC/KeepassDX (password manager for desktop)

Syncthing to synchronize database between devices.

ViMusic is not maintained anymore.

Someone forked it as RiMusic and fixed a lot of bugs with the original version and added the ability to download songs (as opposed to hoping they stay cached)

Thanks. This led me to dual space (https://play.google.com/store/apps/details?id=com.waxmoon.ma.gp https://github.com/WaxMoon/MultiApp). It even seems opensource although I am not sure but the github has a link to the play store.