Macbook Air M2 : issue with external monitor

https://www.sharpnecdisplays.eu/p/datasheet/en/datasheet/rp/ea271q.xhtml

That's a 27" monitor that supports 2560x1440 resolution @ 60 Hz. NEC's site says that it has these connections:

• 1 x DisplayPort
• 1 x DisplayPort out
• 1 x HDMI
• 1 x USB Type C (60 W)
• 1x DVI-D (Dual Link)
• USB ver. 3.1 (3 down / 1 up

The USB-C port is for video input, not just for connecting downstream USB-A ports: "Declutter your desk using the display’s USB Type-C connectivity managing video, audio, power and USB with just a single cable." A Thunderbolt 3 or 4 cable – if not defective – should be more than adequate for making a USB-C to USB-C connection.

Given that this monitor has less than 4K resolution, I'm a little bit surprised that Sonoma is offering you a set of five "Police plus grande" (Larger text) … "Plus d'espace" (More Space) options.

What happens if you

• Click on the Advanced… button
• Enable "Show resolutions as list"; click on Done
• Enable "Show all resolutions"
• Try "2560x1440" and "2560x1440 (low resolution)" (one or both, depending on which shows up)

My monitor is a 4K one (though perhaps not as color-accurate as a NEC EA271Q), and I know that on all five of the simplified "icon" settings, the Mac sends a 4K signal to the monitor. But I'm wondering if perhaps, given that your monitor is a 2.5K one, that some of those choices are mapping to something other than a 2.5K signal.

Note that not all USB-C cables are created equal. You need to verify that the USB-C cable you have specifically states that it supports video. Not all do, especially "charging cables" which generally support only USB2 and some times USB3 which does not support video. If it does not specifically say it supports video, it doesn't.

Search Amazon using "usb-c cable video" and you will find lots to chose from.