From how well they’ve done with their upstreams, like the kernel and Mesa, I expect they will happily accept patches from their downstream

Valve hires lots of developers to improve graphics drivers for all Linux users

SteamOS is currently on kernel 6.1, a lot of the changes they’ve made have gotten merged into upstream which is at 6.6

A few changes they’ve made for their specific hardware have ended up causing regressions for other hardware, so it still needs more code review and testing before everything is completely upstream