The wgpu sources have various comments here and there remarking on how lavapipe doesn't implement Vulkan well enough to fully support WebGPU, but I wonder if that's true any more. Apparently Linux Mesa lavapipe 22.1.2 passes the Vulkan 1.3 CTS.

We should go through wgpu and see what works now and which caveats still apply. It would sure be nice to have lavapipe for software-based testing.