This appears to be a Linux/Proton specific bug, and may not be reproducible on other HW/SW configurations.
When Both Contact Shadows, and HW Anti Aliasing are turned on in game I get a texture bug with human skin that makes it look pitch black outside of some specific artifact that allows the actual skin tones to show through.
System info:
Manjaro Linux / Proton Experimental
AMD Ryzen Threadripper 2950X
31.2 GiB of RAM
AMD Radeon RX 6800 XT