I'm trying to use the shadow catcher option but it simply renders the whole object invisible, not showing the shadows. I created a very simple scene from scratch just to verify and it gives the same results.
I also experience severe issues with Shadow Catchers on macOS (RPR v2.0.52)
A Shadow Catcher sample file attached - this file crashes on macOS.
Shadow catcher setup (turned on for the plane):
Preview render (if it will start) - simply move about in the viewport to crash Blender (I have attached Crash Report Text files):
Final Render does not crash.
However, as stated in the initial report... the output is not quite as expected. The shadow catcher plane has vanished and does not have the correct shadow on it.
If the shadow catcher setting is disabled this is the result of Final Render. You might expect the nice soft shadow to be rendered to the shadow catcher plane.