If I use rulers the GPU preview switches back to CPU and the Illustrator slow down.
If I switch off the rulers and open again the GPU preview will OK.
Mac Mini 2020 M1
Illustrator 25.2.1 and 25.3 BETA
I have a hardware calibrated monitor. This monitor was calibrated last time in Windows and the color profiles were copied from too. When I recalibrate my monitor on Mac this problem not makes slowdown.