It does work, flicking it on now shows my TV as a source in the Sonos appand had my NAS showing (currently off) a month or so ago to test when someone asked the same question. If you search hardware upnp / media server seem to work but software based ones are hit and miss.

beyond that I no idea what the Sonos requirements are, sorry.

Thanks. 

Let's hope somebody here can suggest which upnp server actually works.