Cannot mirror screen on new iMac 2021 to Mac mid 2011(High Sierra. Works in reverse, but not what I want
I want to use my old Mac mid 2011 HighSierra) as a second screen for my new iMac 2021(Monterey). I cannot make this work. I'm using a thunderbolt cable. Somewhat funny, the old Mac will mirror the screen of the new Mac, but not in reverse. I've read every article, but can't make it work. Any help out there?
iMac Line (2012 and Later)