Can I use my Late 2012 27" iMac as a monitor for Mac Mini M3
My late 2012 iMac has a 3.4 GB Quad Core Intel Core I7 processor, 32 GB 1600 MHz DDR3 memory. Graphics is NVIDIA GeForce GTX 680MX 2GB. The machine has a 2.0 Bus.
iMac 27″, macOS 10.15
No, sorry my friend. You cannot use that 2012 iMac as a monitor for your Mac mini.
What Apple used to call Target Display is long dead.
It is no longer supported in hardware nor in software.
You'll need to budget for a regular monitor for your mini. $125-$250 should get you started.