I am under the presumption that the current state of the Intel Arc Alchemist GPUs will likely remain about the same under Mesa even if support is dropped today by Intel. Am I mistaken in the amount of continued driver effort Intel has been putting in for the Mesa GPU drivers?
Obviously if this is true, one should probably remain wary of upcoming Battlemage GPUs.
The best three brands with natively-supported hardware:
Pretty much everything else requires a lot more tinkering than just launching SteamVR/OpenVR applications.
Some helpful links for diagnosing compatibility: