rick-yao Said:
"M1 Air wake up my external display when mac is in sleep mode: my m1 Mac Air device(sleeping) wakes up my external display (dell 2720qm) from time to time. This makes my external display activated and then go black a few seconds later. os version : 11.6 , But I have to say this issue exsists from 11.2"
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Try Reinstalling the macOS:
Being an intermittent issues, start by reinstalling the MacOS. Nothing would be deleted. It's just that items that have become corrupted or deleted, would be replaced or reinstalled back to where they should be. Go Here: How to reinstall macOS from macOS Recovery - Apple Support
Important:
Create a Time Machine Backup, First:
Prior to the re-installation of your macOS, be certain to backup your Mac using a Time Machine Backup. That way, you can have something to restore your Mac from, should anything go wrong with the reinstall. Use an external hard drive that is at least 1.5 the total storage capacity.