[aquabib]

You can install Steam and NVIDIA proprietary drivers just fine on Arch Linux or any other distro, as well.

Ubuntu is the only officially supported distro, as in mentioned in system requirements, just because it's the most ubiquitous distro. It doesn't actually mean you will have any less problems with the problematic Linux games on Ubuntu, than on any other distro.

On Arch, with an NVIDIA card, getting this "all" up and running boils down to: sudo pacman -S steam nvidia

This gives you the most recent NVIDIA driver, 378.13-5.