If your device can already play DSD then you don't need to do the PCM conversion. You may have to turn on the DoP flag under advanced since you previously said you couldn't play 2.0 DSD.
"Mapping 5.0 to 2.0" without going through PCM is not a thing that I know of.
It might be possible for one to discard the 3 unwanted streams but we don't do that and what roon does and doesn't do isn't terribly useful since there are all sorts of things MC can do that roon can't.
Like I said before, Teac plays 2.0 dsf files via network without any additional help... minidlna alone serves those files "as is". "DSD over PCM" flag definitely prevents playback in my setup... Teac would require DoP if the _transport_ is connected via coax/optical/USB -- but not for files served via its LAN or USB drive interface... but that's details pertinent to my specific use case.
Currently, the only possible workaround seems to be @bob's suggestion to turn the conversion on in DSP under DLNA (352.8 KHz work as well, btw, with Teac correctly showing the properties of the stream).
as far as Roon goes: yes, you are right, that is exactly what it does -- drops the channels that the renderer does not have (or, more precisely, it is _one of the two things_ it can do... the second thing being mixing those channels into the L and R of 2.0 setup. User-selectable, of course ;-)) I don't think my use case is unique; and -- IMVHO -- channel downmixing/remapping _without downsampling_ would be a nice feature to implement in JRiver.
second point on Roon is more philosophical, if you will, so feel free to read diagonally
The Interact forums are peppered with references to Roon, comparing it to JRiver; there appears to be no _perfect_ product for every use case. I'm slightly biased towards tinkering (hence MC on a virtual Ubuntu sitting on top of a DIY Debian server with OMV), and my wife prefers "turn-key" solutions -- hence Roon (sitting very comfortably on that same virtual machine, but that's -- again -- details). Since I paid for both products, I am acutely aware of the price difference between MC and Roon, as well as differences in features.
I truly appreciate your efforts to help find the solution for my issue. For now, I'll probably have to simply remember which albums I have in 5.0/5.1 (there's not a whole lot of them in my collection), and choose the audio server (MC v. Roon) accordingly.
Please chime in if you think of any other ideas I can test out.
A