Hi @mattwjj,
Funny enough this my ultimate goal as well (except with server on FreeBSD or FreeNAS).
Please have a look at my linked post, Imported iTunes playlists are not showing in UI.
Firstly, note carefully where iTunes is storing it’s media files especially in the iTunes XML file.
A file stored in /Volumes/Macintosh HD/Users/username/Music/iTunes/ is not the same as a file stored in /Users/username/Music/iTunes/.
Then, make sure your Plex Music library location exactly matches this path otherwise the files will not be found.
After creating a manual playlist you should be able to do an import of iTunes playlists. This brings over play counts and ratings as well.
