Restore fails with error: 'No suitable backups found at given location'

[DDvO]

Trying to migrate apps+data to my new phone, the restore step fails. regardless which storage location I tried on the target (local phone storage or webDAV via the DAVx5 app, which provided further challenges, see https://github.com/seedvault-app/seedvault/issues/85#issuecomment-2170765445). After entering the correct 12-word passphrase that I had used to backup up apps+data on my old phone, I am stuck with this error:

No suitable backups found at given location This is most likely due to a wrong recovery code or storage error.

When I then select "Skip restoring apps", I get

No storage backups found Sorry, but there is nothing that can be restored.

The above error messages are very vague, not giving real info what went wrong why, so I can only guess what went wrong. I suspect a Seedvault bug. It turns out that it is there since more than 3 years: https://www.reddit.com/r/LineageOS/comments/lask4q/no_suitable_backups_found_at_given_location_for/

This makes Seedvault unusable for migrating apps+data to a new phone ☹️