I can confirm that ARC only support 2.0 in my setup. My TV /receiver do not support EARC, though that should be able to forward the signal.
If I put the CC into my yamaha directly I'm getting a 3/2/0 PCM signal (5.0). This is surround and I can hear that over my headphones. However, I also feel that I'm missing some bass compared to my ps4pro destiny 2 gameplay.
Ps4pro gives a 7.1 PCM signal AND supports dolby digital/DTS for ARC/optical paths, that's much better for surround.
Yeah I'm literally able to get surround sound out of everything but stadia. I've never had an issue where I don't get surround sound with my current set-up until stadia. Hopefully this can get updated.
same issue. no 5.1 signal to AVR shows 4K HDR stereo. game shows 4K HDR 5.1.
CCU ethernet to 1Gbps fiber (display shows excellent connection)
CCU into HDCP 2.2 port on AVR
AVR to TV
any other source that plays 5.1 (netflix, amazon, etc) on the CCU plays 5.1 only stadia will not play 5.1.
other LPCM sources play fine even PCM sources play without issue on AVR.