Phoronix published a review on the AMD's Vulkan (Linux) Driver Will Only Work With The AMDGPU Kernel Driver A quote from the article:

I've just received confirmation from AMD that their forthcoming Vulkan driver will only work with the AMDGPU DRM kernel driver. This means that unless this AMDGPU kernel driver is extended to support pre-VI hardware, only the very latest AMD GPUs on Linux will work with Khronos' next-generation API.

Last week I shared a bunch of new details about the AMDGPU / Radeon Linux plans for the year following a briefing with several AMD engineers. One of the follow-up questions I had was whether their Vulkan driver they developed will work with the existing Radeon DRM driver or be limited to the AMDGPU driver.

 AMD's Vulkan (Linux) Driver Will Only Work With The AMDGPU Kernel Driver @ Phoronix