I tried to play 5.1 Flac Files to my Receiver (Hdmi Conection) without sucess. The Songs skips.
When I change from 5.1 to 2.0 in Roon Device Setup, the song plays.
The Pioneer AVR Elite Vsx53 is conected to Win 10 Roon Core Computer via Hdmi, and Pioneer Driver show up in Roons’s Audio Devices.
In the device setup screen, try setting the “Channel Layout” to 7.1 as well as enabling the “Send stereo/mono content as 7.1” and “Swap Rear and Surround Channels”. Let me know if this works for you!