Most app data you cannot back up easily without root anymore. I used to use Titanium but stuff stopped working consistently even with root.
Settings and some apps aside, I otherwise basically do this myself. I keep my last model phone as the fallback and use Syncthing to copy pictures, SMS and call log exports, TOTP exports, Signal backups, and any other useful files automatically to it. Contacts and everything else is cloud already. Would take about 10 minutes to reimport and start using.
I encountered this on a two week old Pixel 7a. I upgraded to 14 when I got it and enabled multiple profiles a few days ago, and last night when I unlocked my phone it just started factory resetting itself all on its own, which was quite shocking. I tried to intervene and cancel it but was left with the boot loop everyone is seeing.
I also encountered various minor launcher issues after I started using the multiple profiles which seems to be related.
My server is not federated but fairly active, and we treat it as ephemeral. We've configured it so anything older than a week or two gets reclaimed automatically, text and media.
Settings and some apps aside, I otherwise basically do this myself. I keep my last model phone as the fallback and use Syncthing to copy pictures, SMS and call log exports, TOTP exports, Signal backups, and any other useful files automatically to it. Contacts and everything else is cloud already. Would take about 10 minutes to reimport and start using.