Answering my own silly question:
“Process .m3u Files” must be set to yes to make Firefly process the XML.
Well, I find this a bit misleading (.xml is not .m3u) but now the playlists show up again.
There is still the issue, that songs with special characters are missing in the playlists:
Here again my setup:
Music Library on a Linux box, managed from iTunes on a Mac over SMB.
a) Firefly on the Mac accessing the Music Library over SMB: Everything works fine (but takes very long to connect to Firefly initially)
b) Firefly on the Linux box accessing the Music Library locally: Songs play well but all songs with special characters get dropped from playlists.
It obviously has something to do, that filenames with special characters look different whether accessed locally or over SMB. If anyone has a solution how to fix this, please leave a message.
As a lot of people use a NSLU with Firefly, I wonder, whether they have the same problem, if they manage their Library remotely via iTunes?
I’m thinking of just buying a second hand Mac Mini installing Firefly along with iTunes on it and replacing my Linuxbox as my Music Server, if I do not get this problem fixed.