Mac communication

You've not given enough information for us to provide a definitive answer. Please carefully read this Apple document on the subject to see how model year, screen size, and operating system constraints effect the use of Target Display Mode.

Only a few Macs made between Late 2009 and Mid 2014 can function as external monitors, and no 2020 Macs can take advantage of any iMac set as an external monitor. The function has been deprecated.

Use your iMac as a display with target display mode - Apple Support

Hi(Bonjour)!

See those articles:

https://applerepairstation.co.uk/Technical%20Desk/use-your-imac-as-a-display-with-target-display-mode/

https://support.apple.com/en-ca/HT202351

Michel B.