Need to Move Lots of Data Between Macs? Try Target Disk Mode - Computer Advantage
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The Ins and Outs of Your iMac's Target Display Mode
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How to Use Your iMac in Target Display Mode - YouTube
TARGET DISPLAY MODE - FIX - MINI DISPLAY PORT 2009-2017 - YouTube
Incase anyone ever needs the answer…I have a 27” 2010 iMac working in Target Display Mode with a M1 MacBook Pro using a miniDP to USB C adaptor that's capable of 4k60Hz.