Like the title says, I'm unable to use the brush tool at all for masking. It is so laggy it freees my screen when i try to possition it over an image. This has been a problem for about a year, but I've ignored it and used Photoshop when a specific need arises. To be clear, the tool is set up correctly... Flow and density at 100% and I'm definitely on Brush (not Erase).
I'm using Lightroom Classic 11.4.1 on a 2017 iMac 5k Retina, 64 GB with the stock