I love the little task bar monitor! Have you checked for a firmware update from Dell? I have known a few over the years to get them and fix odd issues. Most recently is was a pairing my 27” monitors that would randomly wake and search for a signal.
yes the 7” Monitor is 10€ on aliexpress. and is powered by usb (2Watt). The first thing i did was update the fw of the monitor. (have it for 4 weeks now and the thrid FW.
i guess Dell is still updating. but i think it is more of a Bios problem. That it doesn’t support this resolution.
How are you connecting the monitor? If it’s via USB4/thunderbolt check the relevant bios settings, maybe it’s to do with the pre-boot/pre-OS security settings?