Two Monitors (2011 & 2019 iMac, 21.5”)

[Coach29]

Would like to use my 2011 Mac as a second monitor to my 2019 Mac. Thunderbolt 3 (adapter) on the ‘19 - do I use TB2 cable or FireWire (800) on the ‘11?

 

[joevt]

Thunderbolt 2 cable.
https://support.apple.com/en-us/HT204592

I think you can ignore the macOS version requirements mentioned in that support document.

 

[Coach29]

Thank you.