First, sorry for replying so late, but I was waiting for notifications of replies to my question, but I didn’t receive any (don’t know why…).
MusicBrainz Picard installation was from from Canonical repositories.
As suggested, I tried to remove python3-pyqt5.qtmultimedia package and … it worked ! I also tried to reinstall after python3-pyqt5.qtmultimedia, but no surprise, it made the problem reappear.
If living without python3-pyqt5.qtmultimedia package is the solution for MusicBrainz Picard working, I will live without !
Thank you for the help 