Since 10.15.1 it is not possible to use a custom display profile (no matter wich software and hardware was used to create the ICC profile, it also does not matter wich ICC specifications are used). The same profiles worked just fine under 10.15.0 and any previos versions. As a result any one needing a correctly cilibrated and profiled Display is out of luck and stuck with the aweful default profiles the Mac came with, since those - for whatever reason - work just fine. Using a correct (custom) profile results in distorted colors. It seems to have nothing to do with Night Shift, it does not matter if it is turned on or off. My guess would be LUT/Grahpics Cards/Driver problems.
Is there any known fix since it renders using a "Pro" Mac in a professional environment pointless?