I have a NAS acting as a DLNA server at home. VLC installed as a .deb find it, and its files, in the UPnP section of the playlist. The snap version of VLC does not.
I have also suffered this, it seems to be due to the upnp library failing to bind a socket, the following is what appears in the terminal when navigating to the UPnP view.
[00007fc85cc22b30] upnp services discovery: Initializing libupnp on 'default' interface
[00007fc85cc22b30] upnp services discovery error: Initialization failed: UPNP_E_SOCKET_BIND
[00007fc85cc22b30] main services discovery error: no suitable services discovery module
In the call for testing of VLC this issue was commented here Call for testing: VLC 3.0.0-rc1 but it doesn’t appear to be fixed yet :-/ It was suggested that if VLC used a newer upnp build it may work.
is still an issue then …