Plex Server Music Library works fine, as does iTunes Music Library on SoundTouch 10 (latest updates)
I have the "TuneIn" radio channel on my local Plex - plays on Samsung TV and and PC / Plex Client etc without issue
Using the SoundTouch App, you can browse the the "Plex Media Server" (it is a DNLA NAS client), select channels and then TuneIn Radio and any of the radio stations available. Problem is when you do, you briefly see the play/pause controls flash (sometimes) on the app and then the wifi light goes amber on the SoundTouch 10 and the app say "Ready to Play - but nothing playing!
You can reverse out and select Music on the Plex Server and it plays normally. The TuneIn Radio Channel also play normally on all my other devices.