Big Sur broke screen brightness

My Dell Precision 5510, i7-6820HQ, HD 530 and disabled Nvidia M1000M lost screen brightness control after updating from Catalina to Big Sur. After rebooting screen brightness was working normally, but after another reboot, it was gone again. I didn't change anything between boots. I used Dortania Opencore guide. What could cause this?

submitted by /u/Hyoekki
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