Everything is covered here https://android.stackexchange.com/a/213374
Only addition is the "Restore process" chapter.
Google Support makes it sound like you can only restore the backup on setup.
At setup, to restore your data, follow the on-screen steps.
— https://support.google.com/android/answer/2819582?hl=en
But that's not true.
Start (main activity of) com.google.android.apps.restore (display name is "Android Setup" or "Data Restore Tool") ("restore app")
Go to your settings, search for the app's display name, launch the restore app from there.
Download an activity launcher app.
- https://play.google.com/store/apps/details?id=de.szalkowski.activitylauncher
- https://search.f-droid.org/?q=Activity+launcher&lang=en
Proceed the same way within that app to open the restore app.
Throughout the process, only apps that support Googles backup are shown.
Note how apps that you already installed on the phone are listed as "Installed automatically" (as in "pre-installed onto your phone").
I think this makes the restore app ignore these apps and hence also not try to restore their backups.