That’s basically what this is though. From the project page:
Is this official?
No, but it may as well be 99% of the way there. Most of the code and packages, are straight from Valve, with zero possible edits, and the ISO is being built same rootfs bootstrap as all HoloISO installations run.
And also:
I have an NVIDIA G-
No. Not even questionable. If you have an NVIDIA GPU, You’re on your own. Latest Valve updates for Steam client including normal and Jupiter bootstraps have broken gamepadui on NVIDIA GPUs, and if so, no support will be provided for you.
If this was a reimplementation, Nvidia GPUs would work because they’re supported on Arch. But this isn’t, it’s just a repackaging of what Valve has already done.
Proton GE is to Proton what HoloISO is to SteamOS 3, an unofficial repackaging with some small tweaks.