I’m currently using 367.57 driver from Ubuntu.
If I unset DISPLAY with 367.57 driver doesn’t resolve any vulkan symbols. I would think there is demand for vulkan rendering without xserver like there is for OpenGL. My personal setup doesn’t really require this but it would make some thinks easier wih hybrid graphics laptop.
If a newer driver version supports vulkan without display server I would be happy to try to upgrade. My quick internet search didn’t find any hits for vulkan without display server.