The folks Unity3D are currently doing a "HackWeek" when they work on special projects. It looks like the Linux team are working on using SDL instead of X11 directly which will bring Mir & Wayland support amongst other things.
For those that don't know: X11, Mir and Wayland are what allow you to see windows, drag them around and generally do everything on your Linux computer. X11 is really old and Wayland/Mir will eventually replace it.
I follow Unity developer Na'Tosha Bard on twitter, and it has been fun to see the progress on it, here's what they have done so far!
I love that Unity developers do things like this. SDL support should make things like multiple monitor handling much better. That is something I am especially keen for, as multiple monitor handling in a lot of Unity games is often really poor. SDL could also help them improve things like gamepad/controller support too.
Worth noting that these changes may not end up in the official Unity builds, but we can hope it all works out.