We use HDRIBackdrop in Unreal with ray-traced shadows.
We observed for this case the following CC3 Auto-Setup shader problem:

HQ shader: not working, hair is all black
LW shader: not working, hair is all black
Standard shader: working

Do other people have the same issue?
We tested this with Unreal 4.27.2 (1.22 Auto-Setup) and 5.0.1 (1.23 Auto-Setup).
Problem goes away when we turn off ray-traced shadows on the HDRIBackdrop but we need it for the HDR images to automatically cast ground shadows of the characters.