In retrospect, I think you are far better off forking Quake rather than messing with these kinds of 2010 projects which attempt to solve all problems, and do none of them very well.
If that were the case, no automaker or fridge manufacturer that ships Android would be able to, since in so many of their products, you’re not really able to replace the Linux kernel.
The direction of dependency is from your program to the console specific stuff. You can write a platform library which is linked to your program without releasing that library.
> modern boomer shooters
I didn't say for boomer shooters. It's a general 3D game engine.
> just use Unity, Unreal or occasionally Godot instead of the actual Quake engine.
Because they are popular and familiar, not because they did a serious evaluation.
Also my comment was about Irrlicht/Ogre, etc.
I am reasoning with the example of DirectX. You should be able to release a GPL program that uses DirectX, even though nobody has the source code for it.
If some version of that is not right, it's impossible to make a GPL windows or Mac UI application.