RPR 2.2.1, Blender 2.81a, Mac Os 10.15.2, RX 5700 XT
Check this file scene in attachment. This is basic scene where was added some type of snow to Suzanne.
I try to change Principled shader to RPR UBER, but without any luck.
Material nodes that crash RPR Blender:
How it looks in EEVEE (basic scene without any lighting):
I think that this is related to the feeding a ColorRamp into a Displacement node. The v2.2 release notes state, "Fixed an issue of crashing if Color Ramp node was hooked up to displacement," but I am still experiencing a crash connecting these two nodes.