You don't. Google backup is partial and very limited compared to what apple does, plus privacy issues and you don't get access to app folder without root. (I know about adb but then you can't push the files back there). So it's a shitshow as usual with Android, it all depends on the app. My weight lifting app it can backup on Google cloud. Great. My 2Fa on the other hand it only backup to the 'external' storage, need…
I should be able to toss my phone in a river, buy a new one and get it back exactly the way it is.
Syncthing handles the stuff which matters to me, but it can't get apps back exactly the way they were.