It does I play quite a bit of VR on Linux. The only think that does not work is the valve index audio output so I use Bluetooth earbuds

Valve has done a pretty good job. Probably because of their ownership model

Most of the time it is to avoid xyproblem.info

Sorry I can't help with the proxmox stuff but it is absolutely fine to have a qcow2 image on an SSD pool. Modern SSD write endurance is so high as to be a non issue especially in the relatively tiny work loads that HA will put on it

This is huge for me as well and is what will keep me on Ubuntu Server until I have a very very good reason to leave or someone else adds it.

I really like my zigbee thermostats and would recommend them not cloud at all. I have not found a tasmota or esphome compatible thermostat. You could make your our with relative ease use a simple relay board. But I don't think that it would look great