First reported by mbeckh on https://github.com/metabrainz/picard/pull/3512#issuecomment-6560583805
"I have a strong feeling that this PR introduced a bug. It's no longer possible to change the order of cover art providers. If I revert the change in save, the order gets saved. With this change, any changes of order are lost."
I can confirm that I experience the same issue.