How do I set up uPNP ?

I've a new amplifier that supports uPNP and want to connect it to my music library via LMS (7.9.1). But don't really know where to start.
When I select a uPNP input on the amp it immediately finds my router (a TP Link) and goes on to display 4 sub-directories (Music, Videos, Pictures and Browse Folders). I've no idea where it is picking these folders / options from. None of them can be opened.
uPNP is enabled on the router but it does not list any connections.
My music library is stored at /LMS Music Library/Music/Flac

As an aside LMS also runs the Qobuz plugin. Will I be able to stream this in the way I currently do - LMS - Router - Raspbery Pi - Amp (controlled on Ipad using Squeezepad app)

Thanks

Oh, LMS is running on a Mac by the way (Mojave)