Is UPnP a rubish protocol ???

[simbun]

What you're describing is the discovery process, and that depends primarily on your network setup, but also your device and app.

Apart from a problem I had last week where I couldn't see one MinimServer instance from one phone that was on 2.4G, but I could from one that was on 5G (I was setting up a new wireless speaker at the time with the phone on 2.4G so that could have had some affect), I don't think I've had a single problem and I've been running it for over a decade.

I have a Ubiquiti router and access point plus a single Netgear 24 port switch, with MinimServer coming off the switch and have had no problems at all. I have a number of google speakers on a separate vlan with inter-vlan mdns repeating and BubbleUPnP server proxying them as OpenHome renderers and that's also rock solid, apart from when they update, then they seem to change their UDN which means they lose their configuration in BubbleUPnP server.

From what I've seen on these forums, most of the problems seem to originate from ios devices, and the lumin and naim apps.

When your Lumin app can't discover the player have you tried from another app (preferably from another device to rule out the device), or looked at the network traffic to see if it's still broadcasting? Restarting/Rebooting is often the easier "solution" but it's only temporary.