Whenever I try to add the remote feed~fediverse@piefed.social, I get an “unexpected error”. That’s the only feed that does that.
When I try to make a local one by hand, I get the same error but it does create a Feed entry in “My Feeds” but with Instance set to false.

Did something similar happened to you ? I tried to search in the database for a remnant in feed related tables but couldn’t find anything