[steve1977]

I only now discovered that there are quite really great music addons available (Spotify, etc.).

Unfortunately, it appears that Kodi cannot make music addons available over UPNP (i.e., Kodi acting as UPNP server and host the addons). Is this technically not feasible?

[DaveBlake]

Steve, Montellese is the uPNP guy on the team (I think) and he is rather busy at the moment. This means that uPNP is pretty much unsupported for now, so I doubt you will get an answer any time soon.