What do you mean by 'fully'? I mean, with a lot of hard work, sweat, and cursing that comes with making any large game, not to mention a game engine and various

What do you mean by 'fully'? I mean, with a lot of hard work, sweat, and cursing that comes with making any large game, not to mention a game engine and various support infrastructure too, there's at least one existence proof that they're at least 'working': https://kandria.com/ https://kandria.com/ (How much cursing has been done at Windows vs SBCL vs OpenGL vs various libraries, only Shinmera knows. You might like a recent overview he wrote up of some of the development: https://reader.tymoon.eu/article/413 https://reader.tymoon.eu/article/413 When things work well enough that "build with wine" is a viable strategy, that's pretty well in my book.)