Until I got my RPi I used a Kodi box to stream audio. We have a Synology NAS running its own Media Server plus MinimServer.
In Kodi, you set up your UPnP/DLNA server under Music > Files > Add music > Browse > UPnP devices. You can set up multiple ones. We have both of the above.
The audio is then available via HDMI > TV, S/PDIF (Toslink on ours but you might have co-ax), or analogue (ours is 3.5mm).
It works well but one annoyance is that it forces its own sorting order on the DLNA output and I haven't found a way to disable it.
In Kodi you can also enable Apple AirPlay in Settings > Services (this varies a bit according to which Kodi version you are running).
With the RPi we have more options. We currently run Volumio with Kodi as an add-on app. Where would you run Volumio?
Hmm. Not sure I fully get this, sorry.
Two possible setups I'd be interested in:
1) A streamer with solid DLNA performance (Doesn't disappear, fail to advance tracks) to which I can direct BubbleUPnP control point. Would prefer USB asynchronous output for format compatibility, but optical will do 90% of what I need.
2) a streamer with a connected touchscreen and player software that sees Minimserver on the LAN (as well as Tidal and Qobuz), set to autoboot/resume. This would make a nice idiot-proof way for my guests and family members to use my system without a lot of instruction from me on how to select the endpoint, etc.. Same output requirements.
The closest thing, I gather, is a Raspberry Pi running volumio. But, as I say, the reviews have been poor. Obviously a mac mini running audirvana would do very well, but that's much more expensive, and still has to be turned on/off all the time. Also - no touch screens, right? I'm looking for a more dedicated device.