I don’t think that Ropieee even supports the HDMI interface at all at the moment (@spockfish will be able to give the definitive answer). But even if it does, it’s likely that it will be for 2-channel audio only. AFAIK, none of the Linux distros support multichannel audio at the moment. I think we are still in the same situation as two years ago:
My take: Roon has no problem with multichannel music, but computer implementations of HDMI can best be described as funky. I was able to get multichannel working from my Microsoft Surface via HDMI to my Marantz AV8802A with a few work arounds, but I’ve enjoyed multichannel much more since I got an exaSound e38 DAC connected via USB.
I have multichannel working via HDMI from my Roon Rock to my Denon X3400. HDMI is limited to something like 196KHz, so native DSD or even DSD via DoP isn’t possible. Roon downsamples it to 96KHz and sends it out HDMI. It basically works, but not perfectly. I often have issues with the HDMI handshake insisting it’s 2 channel and I have to fuss around to get it to enable 5.1.
Have you tried using Coreelec on the RPI? I had the same issue with my Odroid N2+, when I came across this tutorial:
(this works with any arm board)
Coreelec uses a patched kernel enabling multichannel audio on the N2+, and so far they are the only one afaik who implemented it. It maybe the same for the RPI. Worth a try. Since having installed Coreelec and Roonbridge on my board I can enjoy multichannel audio via HDMI on my N2+ board.
Perhaps for your information:
The okto dac 8 pro (I’ve ordered it some months ago and now I’m waiting…) is shown as ‘DIYINHK DSD DXD 384kHz USB to I2S/DSD’ with USB ID 0x20b1, 0x2009.
The SOtM devices should be able to work with the dac also in using native DSD in multichannel. I don’t know if RoPieee will do work in the same way…