In the past, functional version of the Sonos app(s):

There was an option in the settings menu to enable UPNP functionality. After this was enabled, the UPNP servers on the local network should show up in the Music Source area.

I had turned this on in the past to browse UPnP Libraries that I keep online but don’t merge into my main listening library. They are handy to have when the mode suits us (think Christmas music). I could queue music from these shares indirectly by adding items to my Sonos favorites.

The current versions of the apps do not have this enable/disable setting/feature anymore. Though, because I enabled this in the past, the Windows app still ‘supports’ this. I just turned on an old NAS (you guessed it, with my Christmas collection) with a UPnP service running and it shows up in the Music Source list. 

I know with all the rest that is going on in the Sonos mess this one may not be way up there in the need to fix list but it is a handy feature, so I just wanted to get it out there.

Perhaps it is a separate topic but I set up the UPnP share as an SMB share and added it as a 2nd Library but it does not show up in the Music Sources. I’m wondering if the 2 libraries would be merged into one Index if I were to re-index the original library. There’s no way I’m going to try this given the mess with Compilation album indexing.