I've used EasyTag on my Linux machine to generate a number of M3U playlists. Most work fine in Sonos, but those which reference filenames or directories containing extended UTF-8 characters (é, ü, ß, etc) do not.
These playlists work fine anywhere else I've tried (Banshee Music Player, UPnPlay Android app), and also the directories and filenames are accessible when accessed by other routes in the Sonos controller software itself. The Sonos software also has no trouble with UTF-8 in MP3 tags.
Would it be possible for UTF-8 support to be added?