As nifty as the M4 Macs are, there seems to be a compatibility issue between the computers and ultrawide monitors.
M4 Macs seem to have an issue with ultrawide 5K2K monitors
As noted by many users on the Apple Community forums, Reddit and even corroborated by a 9to5Mac reader, the M4 Macs seem to break support for some ultrawide monitors. More specifically, those with 5K2K (5120 x 2160) resolution.
Per the reports, the M4 Macs don’t display the proper resolution options for these monitors, which in turn makes the interface and text look blurry. These monitors behave correctly with older Intel and Apple Silicon-based Macs, but when connected to an M4 Mac, they no longer work in HiDPI mode – which upscales the interface to make it sharper.
One user offered the following comment as to the issue:
“While I can select the same resolution on my Mac Mini M4, it doesn’t show HiDPI, and it (indeed) looks worse.” said a user who claims that the HiDPI option works when the monitor is connected to their M1 MacBook Pro.
Another user offered the following:
“Same problem here – MacBook Pro M1 Max: no problem. MacBook Pro M4 Max: 3840 x 1620 resolution is missing.”
Some users have been able to enable HiDPI mode with third-party tools such as BetterDisplay, but this causes other drawbacks, such as the refresh rate dropping from 75Hz to 60Hz.
Apple has yet to publicly acknowledge or comment on the issue.
Via 9to5Mac, discussions.apple.com, and Reddit