Both Unity and Unreal Engine are multiplatform enough to support compiling a Linux version of your game just by clicking your mouse -- everything just works out

Both Unity and Unreal Engine are multiplatform enough to support compiling a Linux version of your game just by clicking your mouse -- everything just works out-of-the-box with no extra work needed. That's why there have been so many more Linux games on Steam in the last few years than there ever have before (I remember 10 years ago when the iD Software games were pretty much all we Linux gamers had). It's AAA games that use their own engines and developers that are too lazy to click the Compile for Linux button in Unity that are holding us back.