I use my Android tablet for sheet music. The music often gets annotated during rehearsals, and so it needs to be backed up. I find that SyncThing works great for this, and my backups go to another PC in my house. Since it doesn't require the cloud, I can access it in performance spaces where I can't get WiFi.

Everything else is backed up through their respective services, such as Gmail, and I just don't have an interesting enough digital life to have much else to backup.

Git works fine with Termux.