How do I fix stretched image on external monitor on my Mac?

MacBook, 12 inch, 2017, running Ventura 13.7.6; with an Acer KA242Y monitor

I changed nothing in the hardware, software, or cords, but suddenly the image on the external monitor is stretched so that it is enlarged and distorted. I restarted both the monitor and the Mac, fiddled with the display resolutions in the system settings, but nothing helped.

Can anyone suggest something?

[Re-Titled by Moderator]

Original Title: stretched image on external monitor