[qot]

Thank you for writing this. I use it routinely to back up my phone by mounting it and then simply running rsync.

[replete]

Are you rooted? Have you ever tried restoring a backup in this way?

Backup on android (without Google Services' online) is awful, SeedVault exists but has issues.

[cyberpunk]

Am I missing something? Your phone isn’t using encrypted storage?

[LoganDark]

Encrypted storage is an implementation detail of the filesystem. Once you're at the point of connecting an unlocked phone to a computer running ADB, you can just transfer files and not care about whether or not the underlying data is encrypted at rest.