Setting preferred repo stops updates from first repo

• Device OS and version: /e/OS 3.0.4 (Android 15)
• F-Droid version (in the About screen): 1.23.1
• F-Droid privileged extension version (if installed): /

What did you do? (clear steps if possible)

• Install an app (in this case Catima, not the newest version) from the F-Droid repository
• Add another repo (in this case IzzyOnDroid)
• Set the other repo to preferred (for this app or globally)
• Refresh the repos

What did you expect to see?

I would expect to see the update to the newest version of this app.

What did you see instead?

No update is offered, because the signature is different (F-Droid vs. Dev signature). I have to manually go to the app, (see the warning about signatures), select a different repo and select the newer version to install.

When checking for updates, the preferred repo should be checked first. If there is no update with a matching signature, the other repos should be checked as well.