Some macOS Big Sur users are reporting their Macs running versions 11.1 and 11.2 of the operating system are experiencing ongoing issues with external displays.
MacRumors reports there are multiple posts on the MacRumors forum, Apple Support Communities, Twitter, and Reddit relating the issues users are experiencing.
The multiple issues appear to have originated with the macOS Big Sur 11.1 update, and the 11.2 update has not provided a fix. Some users report that the update has worsened the issue.
The first issue involves a Mac’s USB-C ports failing to recognize external monitors, rendering external displays unusable and unable to connect. The issue apparently affects both DisplayPort and HDMI displays that are connected both directly and through hubs and adapters.
From 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.
The second issue concerns resolution issues that prevent external displays from working at their full 4K 60Hz resolution, instead, the displays are locked at 30Hz. In some cases, a 4K monitor is only recognized as a 1080p monitor.
Reports indicate that many affected users have 16-inch MacBook Pro, but there are reports of other Macs being affected by the same issues. No reliable fixes for these issues have yet been found. Hopefully, macOS Big Sur 11.3 will fix the issues.