Confirmed works with latest 5.1 preview (as of Oct 30). as per [KrasheRXD]. Needs compilation as simply copying the .dll didn’t work for me.
And ditto
"would like to know what raytracing features are locked behind “tier 1.1 raytracing”
As an aiside this change also affects those with slightly newer GPU architecture than GTX Pascal. In my case I have twin Titan Volta cards. Don’t ask how much I paid for them!! 