M3 MacBook Air Recognizing Dual External Displays as One Monitor with Dell - WD22TB4 Thunderbolt 4

Use dual monitors with your MacBook Air with M3 chip - Apple Support

This article seems to implicitly suggest that you should connect the second monitor only after closing the lid.

Just for info, I just bought the same for my Macbook Air M3 16GB. It's for use with 2 x DELL S2721QS monitors.

With the dock, I only have one monitor working so far on HDMI-HDMI (I need another DP-DP cable). I find that with the MBA -> WD22TB -> Dell S2721QS, it works, but only at 30Hz on 4K, and even then, it flickers off and on every 3-5 mins. If I turn it to 4K @ 60Hz (which MacOS offers me), then the monitor can't connect at all, and complains.

With my old setup (MBA --> Apple USB-C to HDMI dongle -> Dell S2721QS), it's stable at 30Hz, and doesn't offer 60Hz.

Now, I did find that with my old setup, the Dell monitor used to flicker with a different HDMI cable. Evidently HDMI cable quality DOES matter when pushing things like this. While the current cable is working OK with the apple adapter, I might see if I can try a 'higher quality' (whatever that is) HDMI cable with the dock, and see if it's stable at 30 or even 60Hz.

Did you solve?

im having the same issue, I have 2 monitors connected via a hub, both monitors come on, I can make one the ‘extension monitor’ but the second doesn’t show up.

if both monitors turn on they both are identical as ‘main display’ and when I close the lid on my air, both go off….