VariableRefresh - visibility, options

Feature Request

I confirm:

• that I haven't found another request for this feature.
• that I have checked whether there are updates for my system available that
  contain this feature already.

Description

VariableRefresh / FreeSync / G-Sync is a complicated beast in linux. There is very little good advice how to enable it, how to enable it on selected 1 display out of N displays (out of which most even not might support VRR). Does it even work in this manner or do you need to disconnect all other non-freesync monitors for it to work? How to enable it in different environments - vulkan, dxvk, gl or whatever etc. etc. Do you need to run the game in Fullscreen mode or is borderless window good enough? Some way to detect what checks or toggles you are missing for it to be on if it's not?
There is no good proof it actually is working (besides your own eyes, which can see whatever you want to see, but not necessarily give you the right answer; and if you are lucky then your hardware monitor settings gui will also show current refresh being variable.).

I understand if this would be way out of Proton scope, but ... can something be done? At least give us HUD overlay option saying if it's ON or OFF right now for the current game. Better if also things that prevent it from working right now. Better yet, if you somewhere give us options to let us force it on or detailed information and commands/script to do so.

Justification [optional]

Because Proton is more gaming oriented? Or maybe it could be integrated into Steam for linux directly? dxvk project? Frankly I have no idea under which tree to bark about this.

No files, tests, or entry points are named. First determine whether Proton, DXVK, Steam for Linux, or the display environment owns VRR status and controls; then narrow the request to a defined visibility or configuration target with a demonstrable way to verify that it is working.