P: Slow UI when using Mac and Custom Display Profile

Who said it was OK? It's a known bug, it's  getting fixed, there's a 'hack' until then as Bill outlined; use sRGB or Adobe RGB (1998) for the display profile. 

Didn't say that. Adobe is working on the custom profile problem but it appears to be complex. As they haven't announced a fix date or for which brand of custom profiles the fix(es) will apply too, in the interim all we can do is either avoid Lightroom V10 or avoid custom profiles. 

So that makes it OK?

Same machine, my son has none of your problems so my guess is that the custom profile is the difference. He doesn't use one.  

Lightroom Classic has been intermittently like walking in drying glue since I guess last fall. I'm on a 2019 16" Macbook Pro, 32GB RAM, 2.3GHZ 8 Core i9, AMD Radeon Pro 5500M. Catalina 10.15.7

Sometimes it performs well, but when it slows down everything is slow. Some things are slower than others in those slow Lightroom times, but even working with keywords can try my patience. The switch to the crop tool seems about the slowest. This relatively high end computer is performing worse with Lightroom than my previous 2013 Macbook Pro did with Lightroom Classic in early 2019. In fact I'm pretty sure it's much worse than the first beta of the first Lightroom I used on my ancient G4 or G5 mac tower 13 or 14 years ago or whenever. If I had to wait for every task with several deep breaths before Lightroom responded, I never would have started using it. I've used every version of Lightroom ever released and it's been fantastic until the last months. Of course I have a custom profile for my monitors, and I need that. I can't go back to before V10 because I've done so much work on the catalog. Quitting and restarting Lightroom sometimes helps for a while. I optimize/backup the catalog about every day.

@Rikk Count me in here too, but downgrading isn't an option because of the 16" mbp performance problems in the older version (though it would also fix the slideshow bug in the other thread).

Color managed workflow is critical, so I guess we're stuck?  I'm rather surprised that this made it through QA without being caught.

yep anything I try and do in the develop Module takes for ages since this upgrade, my work flow is taking substation longer. very frustrating. 

As others have discovered, a bug in macOS was causing some of these problems. Upgrading to 11.2 has been a boon for some of us. 

No inside information, but my instinct (as someone with software development experience) suggests this may be a bug that is triggered by some attribute of the MacOS environment—maybe a MacOS (Metal?) link library—which requires Apple's assistance to fix.  If so, I suspect the lack of transparency from Adobe may reflect its contractual obligations to Apple, a notoriously secretive company.  Several posters here and elsewhere who apparently are working with Adobe subject to nondisclosure agreements have indicated that the issue is being seriously addressed.  I don't know any reason to doubt them.  I'm sticking with a Lightroom rev that works fine in my environment (2013 Mac Pro, MacOS 10.15.7, NEC Spectraview monitors) and I really don't feel seriously inconvenienced as I wait for the problem to be resolved.

A new (at least to me) wrinkle in this saga—I had the same behavior happen yesterday in ACR. I adjusted a slider and my system froze so that I had to do a hard re-boot. Even a force-quit was not possible. 

This is the same behavior I experienced with Lightroom until I disabled GPU acceleration.