Thanks for the follow up. I do appreciate it.
Currently I have JRiver running on my NAS in docker. This is the server for two raspberry pi clients. One raspberry pi is connected to the hifi (for music) and the second connected to the TV (for video and to control audio playback on the hifi). For the clients I have 'show playback zones from the server on the client' and sharing of the media is done by mapping the same network shares on each of the clients (so playback is 'direct').
For DLNA rendering to work each of the clients need media network enabled. For me using JRiver in this way causes instability in both clients. I've experienced random crashes/zones not keeping up what's happening on other clients - either displaying random library content or not showing that there is playback occurring when there is. I've tried every possible combination of setting that I can think of to address this issue (linking zones /groups/ diverting playback etc).
What I am seeking is to have all of the zones that show on the server, including the zones on the clients, to present as DLNA renderers on the server. This is so that external apps eg bubbleupnp or similar can connect to a DLNA renderer on the server only. My hope is that this will address the stability issues I'm experiencing.
Happy to provide further detail if needed of course.