Issues with AMDVLK and some Vulkan apps like gamescope

If you get the following stupid error with gamescope:

% gamescope
No CAP_SYS_NICE, falling back to regular-priority compute and threads.
Performance will be affected.
vulkan: selecting physical device 'AMD Radeon RX Vega': queue family 1
vulkan: physical device does not support DRM format modifiers
vulkan: physical device doesn't support VK_EXT_physical_device_drm
Failed to initialize Vulkan

Then you need to force RADv (whatever that means.) Something to do with a Vulkan layer doing something stupid.

To force RADV instead of AMDVLK:

VK_ICD_FILENAMES=/usr/share/vulkan/icd.d/radeon_icd.i686.json:/usr/share/vulkan/icd.d/radeon_icd.x86_64.json gamescope  --  

I found that in one Unity title--without using gamescope on it--this causes the game to go from 99% utilization with potato graphics to 70% utilization at full graphics.