How do vulkan games like doom eternal run on xbox?

doom eternal runs open GL on the xbox, you get the option on pc to run vulkan or open gl

You mean DirectX?

Because Vulkan basically an upgraded version of opengl and opengl also doesn't support UWP unless you port it:

Port a simple OpenGL ES 2.0 renderer to Direct3D 11 - UWP applications | Microsoft Docs

Pretty sure they're not using Vulkan on Xbox.

How they run depends on what console you're using. On Series X they're excellent, and Doom Eternal even has raytraced reflections on the Series X hardware. The RT can drop the FPS to just below 60 occasionally, but it's largely flawless.

On the now older Xbox One S their resolution is limited to around 900P, but they run much smoother and in higher res on the One X and Series X.

If you've got a Series X, Doom 2016, Doom Eternal, Wolfenstein II The New Colossus and Wolfenstein Youngblood play really well. No major performance issues. Digital Foundry on YouTube have conducted extensive tests on these games. I would check them out.

Doom Eternal Next-Gen Upgrade: PS5 vs Xbox Series X/ Series S - All Modes Tested

So, you mean it could use vulkan

SIMULTANEOUSLY with dx12 on xbox and still manage to run because some vulkan functions are compatible with UWP?

They would likely use a DX12 renderer instead. Games aren’t necessarily written on a single API. Many games support DZx11 and 12 for example, or OpenGL

No one with that information posts here or would likely be allowed to share it if they did.