retroarch supports it as a graphics driver but it's used for simple blitting to the screen, so no perceivable advantage in 2d emulators. another side effect is that the usual GLSL shaders we use will not work with vulkan - you have to use SLANG ones.
3d cores and standalone emulators may have vulkan implementations, which would take advantage of the new speed/features. lr-parallel would be a fun experiment (though i expect not viable at all). duckstation, beetle-psx, flycast, ppsspp, and dolphin are potentially viable ones that i can think of.
another issue is, does the vulkan driver still need X? that's not ideal.