i don't have anything useful for you, except to say that this should or can be a working setup.
> I've got a setup with two sound cards: the on-board sound chip, and the > graphics card (a Radeon RX550). These both seem to be dectected (after > adding the HDAUDIO_ENABLE_HDMI option to the kernel config), as the > dmesg shows: this works for me, across a couple of systems (same GPU), the last few years. my setup was haswell + supermicro motherboard, and is now zen2 + asus m/b, both with radeonhd 5450. my mixerctl, audioctl, and audiocfg output match yours almost identically except i'm missing the 8 channel options, and my mixerctl has just this: outputs.dacsel=HDMI00 connected to a dell ultrasharp lcd (both 2415 and 2715 models) using it's audio jack connected to a 2.1 speaker setup. i last updated my kernel about 3 weeks ago. .mrg.
