Back when that empty first guide was created, I tried something similar to this. SteamVR on Linux wouldn't recognize VaM at all as a VR application, even with the same Steam configuration you suggested, and it wouldn't display in VR. The new SteamVR updates Valve has been pushing, or some other Linux change, appears to have fixed that. I can confirm I can get into VR with the new SteamVR runtime. Audio on Linux in VR is a separate issue. I've used multiple headsets with Linux and AMD and NVIDIA GPUs. My experience was that AMD consistently worked for video and audio, and I consistently cannot get audio to work through an NVIDIA GPU.
There are multiple discussions on other forums about workarounds to getting audio to work with an NVIDIA GPU, but I never had luck with them. I use a separate wireless headset for audio, instead. If I don't care about the latency of bluetooth, I use wireless earbuds. The audio quality is higher, anyway, than what you get with most VR headsets. I'll probably switch back to an AMD GPU next upgrade for Linux HDR and VR. You can get HDR on Linux now if you use Valve's Gamescope (I tested succesfully on a secondary computer with an older gen AMD GPU), and VR was a better experience on Linux before I switched to my 4090.
