Epic is not making RTX chips. Why banned? Waiting for AMD cards support in UE4.
About Preview 5 … there are all bad, really bad. Not even skylight makes overbright and BP_skysphere gives black. After datasmith import UE4 crashes and after restart editor wrote there are no objects (object dummies are in scene) here.
Back to preview 4. Or looking to Cryengine. 