I just changed the hardware by replacing my iMac 27 "with a Mac mini M1 paired with an LG Ultrafine 5K display. The result is really great, unfortunately I am facing an extremely annoying problem with the color management.
For some reason that I do not know, without me modifying anything (default Lightroom settings, default screen settings, default color profile), it happens that the colors of my images change on their own, when I zoom in and zoom out in the image, when I move around in the image, etc. The image gains or loses saturation, quite randomly. It is very disturbing. For your information, I am experiencing the exact same problem on Photoshop.
I tried to change the color profile of the screen, I tested several, the problem is still present, the colors change on their own.
I made a little video to show you what's going on. Hope the quality will be good enough that you can see the change in the colors: https://youtu.be/3ov3yVABwM8
First, try disabling GPU in the preferences (Preformance tab). Any better? If not, recalibrate and build a new ICC display profile, the old one might be corrupted. If you are using software/hardware for this task, be sure the software is set to build a matrix not LUT profile, Version 2 not Version 4 profile. If turning OFF GPU works, it's a GPU bug and you need to contact the manufacturer or find out if there's an updated driver for it. Also see: https://helpx.adobe.com/photoshop/kb/acr-gpu-faq.html
Author “Color Management for Photographers" & "Photoshop CC Color Management" (pluralsight.com)
If I completely disable the GPU, I now notice a strong lack of fluidity when zooming or moving around an image. On the other hand, if I choose "Custom" and that I check only "Use GPU for display", leaving "Use GPU for image processing" unchecked, it is smooth. I will test this setting for a few days and tell you if I still see the color problem.