When I have the beta site set in Options/General/Server address, I can't login to my MB account in Picard. Whilst the rights request in the browser proceeds as expected (showing; "Authentication successful, you can close this window now.") there's a red error in Picard options: "Login failed: Unexpected request error (HTTP code 200)". I can login ok when I switch to the normal site.

The logs show the following:

E: 21:39:10,027 webservice._handle_reply:574: Unable to parse the response for https://beta.musicbrainz.org/oauth2/token -> Expecting value: line 1 column 1 (char 0)

E: 21:39:10,027 oauth.on_exchange_authorization_code_finished:339: OAuth: authorization_code exchange failed: b''