I am running MC 2022.7 on an old but good 27" iMac from something like late 2013. It has Thunderbolt and USB outputs, no HDMI.  My simple question is, how do I attach a cient monitor?

Thanks,

marluc

Any of the older BMD Decklink Mini Monitors or original AJA T-taps will do fine. Note that any such hardware device will force MC to send both picture and sound out through the same device. So you won't be able to use the iMacs internal sound card as a playback device at the same time.