in Unreal 4.5 Doc Roadmap
5.4 marks the experimental release for Vulkan ray tracing features at parity with DX12, including on the Linux platform. This will allow the full suite of ray tracing features to be used, including Hit Lighting mode in Lumen and Path Tracing. As an experimental release, it is expected that there will be bugs and other errors - and should not be relied upon for production.
But i use Linux and Path Tracing and GPU Lightmass Still Not Work At All in All Distros …
is That Right or i miss something ?