Unreal Engine 4 now has support for Linux with the update to 4.1
https://www.unrealengine.com/blog/41-update-preview
Folks have been asking about our early Linux efforts and support for Valve’s SteamOS and Steam Machines. We have good news for you! The 4.1 source code has initial support for running and packaging games for Linux and SteamOS. We love Linux!
So, we have the Cryengine, Valve's Source (and unless they go crazy, Source2 too) and now UE4. maybe Valve will fail with its Steam Machines, but Linux users sure will benefit from their effort!
Please excuse my bad English.
Currently gaming on a PC with an i5-4670k@stock (for now), 16Gb RAM 1600 MHz and a GTX 1070
Steam / Live / NNID : jonxiquet Add me if you want, but I'm a single player gamer.