There’s a few things I backup from my phone.

• Music downloaded from Seeker
• Youtube audio downloaded from YTDLnis
• Backups of Termux
• Notes in plain text
• Backups from certain apps that make their own backup data
• Pictures that I have sorted and want to saved

I have an Android phone so I use Termux as a terminal emulator. I use ssh and passwordless keys to make transfers simpler and quicker.

Although this is closer to a backup process and not like SyncThing where it’s syncing a folder between two devices. I don’t believe rsync is capable of acting like SyncThing but I’m tempted to dig into rsync more and see if I can put something basic together one day.