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.
iMac 27 2010 2.93 Ghz intel core i7
Apple iMac 27" - Mid 2010 Reviews, Pros and Cons | TechSpot
iMac 27-inch Mid-2010 Not Displaying : r/mac
Imac 27 i7 mid-2010 €350 №4531814 in Limassol - Desktops, servers - sell, buy, ads on bazaraki.com
Mid 2010 imac for Sale | Desktop & Workstation Computers | Gumtree
Apple iMac 21.5-inch 3.2GHz Core i3 (Mid 2010) MC509LL/A | mac of all trades
iMac Core I7 Review (Mid 2010) - SlashGear
Internal SSD DIY KIT for All Apple 27" iMac 2010 Models