Vulkan is a rendering technology, Unreal is an engine, that can render using Vulkan under the hood. You can absolutely do this in Unreal. I implemented this at Cruise using UE4 for integration testing, and it worked great for inference (we weren't doing training on sim at that point, but I was pushing for it! There was a paper out in 2018 or so that showed mixing in a bit of simulated data had an outside positive impact on the outputted model). There are companies out there right now doing this with even more modern renderers. I can't comment on how much the rendering realism gap matters here. I think there's some people out there using a variant of lower quality rendering + some kind of diffusion to get "better" images without having to do detailed modeling/lighting for their sims (fuzzy memory, I don't have a source on this).