target display mode doesn't work imac 2020 to iMac late 2009
solution to connect a old iMac 2009 as secondary display for a new iMac2020 A (target display mode doesn't work with a USB-C original Apple adapter cable to mini-displayport) )
Welcome.
Per this Apple article, you cannot. Apple dropped the ability from 2020 Macs to see an iMac as an external monitor.
Use your iMac as a display with target display mode - Apple Support
That said, if you look in the iMac forums, there is a post by someone claiming to have made TDM work from a 2020 Mac to a 2009 iMac. Others responding say they cannot get it to work.
👉🏻 Remember, a Late 2009 iMac must be the 27-inch version, not the 21.5-inch. The smaller screen was only supported for TDM from 2011 to Mid 2014.
You posted in a forum for Apple hardware made before 1998. No one sees posts here. I will ask the Hosts to move you to the iMac forum.
