It appears that with some 5120x2160 ultrawide displays, the M4 Mac is not correctly detecting “HiDPI” mode, making display scaling unavailable, forcing users to choose between too-low and too-high resolutions.
Not sure what the cause is at this time, but some have reported that the BetterDisplay utility can be used as a successful workaround.
Aww, man, I had been considering one of those 5K2K screens, if only I could see one in person, but the fact that they may be quirky with macOS is a strike against.
Do you mean like this?
An ultrawide virtual screen via my MacBook Pro and an Apple Vision Pro.
Hah! No, the Vision Pro still costs about three times as much as a 5K2K display like this one.
https://www.bhphotovideo.com/c/product/1814581-REG/dell_u4025qw_40_curved_5k_120hz.html