Mac Mini M1 ChipSource: Apple

What you need to know

  • macOS Big Sur 11.1 and 11.2 are causing issues for external displays.
  • Displays either won't work or can't show their full resolution.

As reported by MacRumors, some macOS Big Sur users who have upgraded to 11.1 and 11.2 are having continuous issues when hooking up their Macs to an external display. The issue appears to have been introduced in macOS Big Sur 11.1 and, unfortunately, the 11.2 update has either not fixed or, in certain cases, worsened it.

The first issue causes external displays not to be recognized by the USB-C port on the Mac, rendering the display useless.

The first issue causes USB-C ports to fail to recognize external monitors, rendering external displays unusable and unable to connect. This appears to be affecting both DisplayPort and HDMI displays connected directly and through hubs and adapters.

MacRumors says they experienced the issue themselves after upgrading a MacBook Pro to macOS Big Sur 11.2. Another user posted about the issue on Reddit:

Upgrading to 11.2 broke my second external monitor connection. Primary monitor LG Ultrafine 4k (Mac version) connected via Thunderbolt. Secondary monitor (same model) connected via HDMI->DisplayPort adapter (BENFEI), then DisplayPort->USB-C cable no longer works after updating (worked fine on 11.1 before updating). macOS appears to recognize the monitor and resolution, as it is shown in display settings, and Apple Support was able to remove into my computer and see both screens. It's almost as if the signal for the monitor to turn on is not being sent.

Benq Designvue 4KSource: iMore

The second issue affects the ability of the external display to show content in full 4K 60Hz resolution.

The second issue results in resolution issues with external displays unable to work at a full 4K 60Hz resolution, instead locked at 30Hz. In some cases, a 4K monitor is only recognized as a 1080p monitor.

The macOS Big Sur 11.3 developer beta released yesterday and has not appeared to fix the issue either. However, there is plenty of time between now and the 11.3 public release, so hopefully, Apple will address it by then.