Top of this list used to be particular versions of Ubuntu
Summary: GNU/Linux "market share" in Steam grew by a quarter this past year, boosted by SteamOS perhaps, but watch the trends in distributions; even the Ubuntu-based distros aren't near the top (and SteamOS moved from Debian to Arch, so expect Ubuntu to stagnate further)
We find it kind of funny if not ironic that this site, originally an American site, got legal harassment only from Americans and only months after it had moved to the UK