I know this might not be a supported use case, but I wanna to share my experience with the UPNP setup using Volumio release 3.
I have a USB Audioquest DragonFly 1.5 connected to my RPI 4 running Volumio 2.917. My Dac is not a full MQA unfolder, only an MQA render device.
As Volumio can’t unfold MQA, I’m using another software to connect to Tidal and play tracks. On that other software, I set the output for UPNP Volumio. I’m using Volumio as a kind of transport node between my laptop and my stereo system. Volumio is there to act as a sort of “gateway” between my Lan and my usb Dac.
Works fine until I upgraded to Volumio 3.
With Volumio 3, I got some sluggish performance, can take up to 30 seconds to load up the first track. After two or three tracks, the link between both devices (my other software and Volumio) seems to be broken. I can’t play any new tracks, the track won’t never start.
Rebooting the RPI fix the issue for two, or three tracks, as the same issue start again.
Went back to Volumio 2.917-2021-10-06 and works fine.