Devs don't support anything, they target Windows as if Proton did not exist.
It is up to Valve to make it work.
It is a loss for GNU/Linux as gamming platform.
Do you think anyone would be paying for Nintendo and PlayStation consoles, if they were running XBox OS translations, instead of having the games natively target them?
That is why all those cheap Chinese handhelds never go nowhere, being basically MAME devices.