imac as second screeen

Would like to use a iMac late 2012 21.5" running Catalina 10.15.7 as a second screen or mirrored screen for a 2020 Mac book air retina 13" running Monterey 12.6.

Mac air has 'thunderbolt 3" ports aka USB-C.

The iMac has: USB 3.0 ports and "thunderbolt" ports.

I have the dongle for the MacBook to communicate with thunderbolt 2.

When I connect the two machines nothing happens.

Read that maybe recently with OS changes the feature is no longer available to use the old late 2012 iMac as a second screen.

Is it still possible to use the iMac late 2012 running Catalina 10.15.7 as a second screen? if so, how?

I have tried with no luck.

thank you.