Did you ever find a solution for the HLOD build times?
I tried 5.6 and it has the same issue. But looking at HLOD build logs it’s because our compile shader compilation is crashing and it gets put back on a much slower legacy version.
My i9 13th Gen is affected by this 20+ mins to finish
My i9 10th Gen is not affected 40 seconds to finish and correctly compiled so it seems to be related to hardware and not software for only newer hardware. If you make a sample project and build the standard open world starter map it breaks reguardless. Only on a much older CPU is it fine