Version 2.2 stops the Classical Extras plugin from functioning correctly (even after the v2.0.6 fix)
I have raised a bug report, https://tickets.metabrainz.org/browse/PICARD-1615 :
Previous versions to 2.2 allowed metadata to contain dictionaries. E.g. a plugin could add a metadata item {‘a’: ‘Apple’, ‘b’: ‘Banana’}. Version 2.2 strips this to just a list of the keys - i.e. [‘a’, ‘b’], losing all the values.
EDIT: Having fixed this, it is apparent that there are multiple other issues with Classical Extras compatibility with Picard v2.2. My recommendation is that Classical Extras users should not update to Picard 2.2 until I give the all-clear.