Quest is part of Meta, not Valve / Steam, and thats why I have two.

now take all this back to the first post I had and you see why I said that the whole thing is rather pointless. Yes, there is a thing called OpenXR that almost all VR headsets use for their frameworks, it does not matter as long as each framework is tailored towards a specific headseat - you do not have a choice. and that's it, really.

Yes and no. PimaxXR is not made by Pimax. Someone just decided to make it on their own. There's nothing stopping people from doing the same for other headsets.

Goldsource - no.
Source - yes.

So basically you can run:
Half-Life 1: Source
Half-Life 2
Half-Life 2: Episode One
Half-Life 2: Episode Two

But you cannot run Half-Life 1 and its expansions lol.

You may be able to run Portal 1 too.
It's the exact opposite lol.

For the steam tainted ver of HL1 you can use:
Revolution steam emu (v4554) (XP)
or
Goldberg (Newer than v4554) (XP+) (XP w/ OneCoreAPI files)
or
Xash3D (Use PreFWGS ver for XP and below)

With revemu or Xash3d then you are good to go for XP+ (possibly less than with Xash3D or kernelex with revemu).
For Vista and above you can use Goldberg but for XP you'll need to use the ws2_32 files from OneCoreAPI or possibly the Goldberg XP fork.