Screen flickering on M1 mini with Dell U2718Q

[pshufd]

I switched out my Dell U2720Q (27 inch Ultrasharp 4k) with a Dell U2718Q on my M1 Mac mini as I wanted more USB-A ports off the mini (the U2720Q is USB-C while the U2718Q is USB-A) and I noticed that the screen flickers with the U2718Q. The hookup is with a high-quality HDMI cable as the USB-C port goes to another U2718Q and that display is fine. I rechecked the cables and then played around with the monitor settings and find that turning on HDR got rid of the flicker.

I've seen a lot of reports of black screen, flickering and other issues with external displays so all I can say is check your cables, make sure everything is seated well, and play around with monitor settings.

 

[CheMillan]

Had the same problem. My Mini was connected to a Dell 34” U3415W curved monitor set at 3440x1440 native resolution and 60hz refresh rate using the HDMI to HDMI cable that came with the monitor. The display was flickering very fast after wake from sleep. To solved the problem I shutdown the Mini, disconnected the HDMI to HDMI cable that came with the monitor, got a different cable, a Uni USB-C to DisplayPort cable to reconnect the Dell monitor, then booted the Mini. The flickering stopped. Now my Mini boots, restarts, and wakes from sleep as normal with no display flickering. In System Preferences > Energy, “turn display off after” is set to NEVER. So far so good.

 

[pshufd]

Had the same problem. My Mini was connected to a Dell 34” U3415W curved monitor set at 3440x1440 native resolution and 60hz refresh rate using the HDMI to HDMI cable that came with the monitor. The display was flickering very fast after wake from sleep. To solved the problem I shutdown the Mini, disconnected the HDMI to HDMI cable that came with the monitor, got a different cable, a Uni USB-C to DisplayPort cable to reconnect the Dell monitor, then booted the Mini. The flickering stopped. Now my Mini boots, restarts, and wakes from sleep as normal with no display flickering. In System Preferences > Energy, “turn display off after” is set to NEVER. So far so good.

That explains why I only see it on the HDMI port side. I guess it would help if Apple gave us another USB-C port on the mini as they do on the 2021 MacBook Pros. Or they could fix the HDMI port or processing. I am happy with this solution but some monitors out there may not have all of the options that the Ultrasharps have.

 

[pshufd]

This did not fix the problem as it came back. I did a full reset of the monitor and it ran fine for a while and then it came back. I tried removing devices off the the USB hub (shouldn't really matter as the circuitry is separate) and that did not help. This morning I replaced the 9-foot cable with a 6-foot cable and we'll see if that fixes the problem. The 9-foot cable is a heavy duty cable but perhaps run length is a problem with HDMI and 4k.