Stephan-P Expect app builds to differ between F-droid and the github releases that obtanium fetches, in which case you will have to uninstall the app first and reinstall afterwards.
In order to keep your data, you will need the app's export/import if available.
(I went this route when replacing F-droid with Obtainium)
So I actually have to uninstall every app and reinstall it? I want to switch, but that would be a major inconvenience for me. I just want to be notified for new updates because Aurora Store doesn't notify and I've had app problems because I didn't know they needed to be updated (they were many updates behind!).