External displays
Can I use my late 2009 21.5" iMac as an external display for a 2018 Mac Mini? What connections/adapters would be required if this is possible?
iMac, macOS 10.12
Question marked as
Nope, sorry...
Note: Target Display Mode isn’t supported on iMac models with Retina display. Only iMac (27-inch, Late 2009), iMac (27-inch, Mid 2010), and iMac (Mid 2011 to Mid 2014) support Target Display Mode.
https://support.apple.com/guide/mac-help/use-an-imac-as-a-display-mh30822/mac