iMac 27", late 2012
can i use my iMac 27", late 2012, as a second monitor for my new iMac 24", 2021?
iMac 27″, macOS 10.15
No, please refer to Target Display Mode. Macs are computers, they are not external displays for other devices. If your new Mac has a need for an external display, please buy one. You will find this solution to be extremely reliable, less expensive than expensive cabling and simple to setup and maintain.