So I talked to Yamaha/Steinberg support - 6/2020. They confirmed the UR824 WASAPI interface is stereo only. I requested that the person I was talking to put in a request to development to enhance the driver for multi-channel. He said he would send me an email as to whether the request was accepted or rejected. I have not seen anything after a number of days, but perhaps I’ll still get a response (expecting a reject).
Interestingly, in my experience, the UR824 WASAPI does support any Windows Audio stream through WASAPI concurrently with Protools owning the ASIO interface (this is unusual, I think). The stereo WASAPI stream comes into the UR824 dspMixFx on the Mix 1 DAW Channel and shows up on outputs 1/2. This seems to be sum’ed with whatever protools is sending to output 1/2.
I have downloaded JRiver Media Center 26.0.80 (MC) and have confirmed that it will provide a WMD interface that can be directed to the UR824 ASIO interface. If you make that you’re windows default audio interface, you can configure MC and Windows to play 2.0, 5.1 or 7.1 audio (assuming you’ve got speakers hooked up). Have tried Neflix 5.1 video/audio, Spotify 5.1 audio, iTunes 2.0. The MC implementation at the the version indicated only creates the audio connection for WMD audio when there is a stream present - it takes a few seconds and generally that makes it miss any ‘beeps’ that an application might generate. If you have a stream running (e.g. Spotify), any beeps do get through because the running stream keeps the connection open. FWIW - I like JRiver so far a lot better than iTunes or Windows Media Player. It costs $50 (I think) - still on the 30 day evaluation period.
I’m thinking I can use the UR824 WASAPI for general computer work where I want to hear my apps ‘beeps’ and/or listen to 2.0 media. This could include using MC as a media player driving to the UR824 WASAPI. For 5.1 or 7.1 media, I could switch to the MC WDM as the default audio device. This is all done in Windows Control Panel>Sound and MC>Player>Playback Options: Audio Device - just select the interface you want as the default in Windows and the output you want in MC. Minor pain, but not too bad.
I have determined that MC and Protools do both try to reserve the ASIO interface. I have not worked through any resolution of that, but I assume that you can run one or the other and it should work (possibly needs a reboot - but haven’t check that out yet). If you need more details, see: