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):