That’s not true. Some of their developers dedicated time they could use however they wanted to work on the port.
Only a subset of .NET is actually available cross-platform. There is no good .NET-native GUI solution besides WPF, which they appear to be using for the editor.
Unity and UE4 implement their own GUI frameworks (for better and worse) which makes them more portable, but as it has already been said, these Linux editors are more like “pet projects” of their respective developers, they’re not officially supported.
Given the fact that game development itself is extremely Windows-centric these days (all of the console SDKs are based on it), it would be very unwise (from a business standpoint) to spend time on a Linux port of the editor at this stage.
I don’t think anybody really cares at this point. The forums are always full of Linux users that ask about ports of most any piece of software, but then that “demand” rarely translates into profit. Where are the success stories?
A bit late but good new for us, website revamped with new version 1.8 of Xenko. Support VR, PBR Materials, Support Vulkan and directx 12 (!?), SSAO, CEL Shading… Still beta but great evolution !
Happy coding !