I've upgraded my desk station from MC 26.x (French version) to 27.0.20 (French version) last week. The main server as well as my laptop still use MC 26.x.
Everything is fine except a few translation errors/omissions and a very annoying behavior with cover art.
It displays properly at the top the MC window as well as close to the file names but not in views (cf. attached screenshot).
At the system level, all audio file (flac/ape/wav...) miniatures have disappeared, replaced by application icons. Audio files are properly tagged using dBpoweramp and have embedded folder.jpg miniatures. Folders and other file types still show proper miniatures.
This problem seems to be custom handler related, but, as I've upgraded MC as well as dBpoweramp (from 16.x to 17.2) the same day, this could be caused by the latter or could be a conflict between custom handlers.
I've cleaned the miniatures cache, done an in-place repair of Windows 10 Pro, uninstalled and reinstalled MC as well as dBpoweramp. Still the same problem.
I'm in contact with Spoon at Illustrate who's currently investigating this problem on the dBpoweramp side.