Linux surpasses the Mac among Steam gamers

Finally Linux will get the same respect Mac gets from gaming publishers.

As in: "If we built it in OpenGL/Vulkan, we will attempt to compile it on Mac; and if it works, release it in a mostly untested form"?

At least Vulkan is a first-class citizen on Linux, so the aforementioned issues are even less headache-filled.

And yet, game developers don't care about Vulkan since it's non-existent on actual gaming platforms that bring in money

Red Dead Redemption 2 has a Vulkan renderer. Doom and the new Wolfenstein games, too.

Also the Nintendo Switch supports Vulkan.

Yes. Some games have a Vulkan renderer (probably because they can afford to).

This is a good table for Vulkan support across platforms: https://www.ravbug.com/graphics/

And on Linux your best bet is to run DirectX through compatibility software like what SteamDeck does.

It's 2023. Pretty much everyone is using Unreal Engine, Unity or Godot for the bravest. Custom renderers are a thing of the past. The reason game developers don't release on macOS and Linux is the costs of testing and supporting the platforms, not the availability of the renderers.