Hi. I might have been a bit vague in my original post. With "does your LG UP850-W monitor work under macOS 12.5", I meant: can you use the monitor with your Mac Mini via an USB-C connection without getting those pesky "no signal found-messages"? I had severe problems with earlier versions of macOS (prior to 12.2), but have been able to have the Mac Mini connected to this monitor without any loss of signal. But, I do want to update to the latest version of macOS, but of course don't want to experience the same problems I (and many others) had earlier.
And yes – I need to connect the monitor via USB-C since I have 2 PC:s simultaneously connected to the very same monitor to be able to hot switch between whatever computer I want to work on.
As in regards to your own question: yes, I see a difference in the last sRGB vs. P3-display section on that website. Running Safari. Clicking on the P3-link reveals a more saturated/vibrant image.