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Seedvault does not suck! It is actually very good, especially with the recent addition of D2D backups which backup all app's data, at least all apps that have been active in the past while! You do need to learn how to use it, and have patience. It will now backup and restore app data even to apps where doing that will make the app crash and only way to fix is reinstalling the app. (financial apps, Proton apps, etc.) You need to do an APK only backup for those apps separately using any app from the Play Store or F-Droid. I recommend App Manager from the later, it;s what I use.
Seedvault may fail backup a few times, just restart it! wait for it to finish completely. If it finishes o an automatic backup and you switched to D2D backups, do it again manually! Then once it finishes your manual backup (you can turn storage backup off for the subsequent backups if you want but leaving it on it just seems to skip storage backup after the scan if nothing has changed), create a new user profile, and at the end of the setup wizard restore your new backup to check it. Make sure all apps are restoring, After 20 of them are OK, just hit back and go to start system so you can go back to Primary profile and delete the test profile.
Congrats! Your backup will now definitely work when needed, and has a lot of app data backed up! Transfer the APK's backup you made with App Manager, Swift Backup, or whatever (those two work great, but App Manager's my favorite) to the same USB drive and there you go!
Oh, and never back up with Seedvault to internal storage!! It is the worst thing to do! Useless for restoring later from there, and can be corrupted if you move them to USB later. Only backup to USB unless you have a stable WebDav server.
That's it! Crash course in how to make Seedvault a valuable tool and how it doesn't suck... if you put some time and actual effort into it. No it isn't an app that "Just Works." So learn how it works! It's not that hard... No it's not like iOS where it's just click and works there are quirks. So spend time and use a bit of mental energy and work out how you can make this powerful tool work for you!