Valve Index, Varjo, and others use Valve's OpenVR standard. Anything using OpenVR usually requires that you have Valve's tracking lighthouses which you can purchase on Steam. As for Linux, I know OpenVR is Linux compatible and some games work on Steam for Linux, but I haven't tried it. I really like what Valve is trying to do. All the hardware is mix and match. If it works on OpenVR, then you can mix and match headsets/controllers. It's modular the way hardware should be.