I got Volumio 2.001 to function for Web Radio, Music Library ( NAS ) and Spotify, except for the volume settings.
I have now tried with all dev releases ( just now 2.024 ) and volume settings functions now for Web Radio and Music Library.
But when selecting Spotify it looks like the Digi+ is disconnected. The led on the optical interface is not on.
No errors are printed out and the Playback page shows that Spotify is playing.
When changing back to Web Radio or Music Library, Digi+ connects and it functions again.