This doesn't work for me as the Music app for MacOS doesn't produce a library like the one iTunes produced, and MC 30 won't accept an .XML file from MacOS's Music app, claiming it's not a valid .xml file.
Incidentally, I transfered a small, individual .m3u playlist saved by Music to MC 30. MC 30 renamed one of the song tracks so it has the same title and artist as the file next to it!
Since your instructions don't work with the MacOS Music app, I decided to see if the playist .m3u files produced by beaTunes5 when synchronizing with Music are transportable to MC 30. I am synchronizing beaTunes5 with Music as we speak...