They do more high performance graphics than the large majority of GNU/Linux "gamming" environments.

Apple is not killing anything, anyone that has a name on the game industry already supports Metal, because professional game studios care about performance and productive tooling not about API religion wars.

Game consoles, outsolding any Linux based platform, also don't support Vulkan, so they are also killing gamming?

Yes, Switch does Vulkan, but their main 3D API is NVN and most of their titles are being done in Unity/Unreal, with Unity already having over 50% of Switch titles.