Old iMac for a monitor
Can I use my 2012 iMac For a monitor using a new Mac mini
iMac 27″, macOS 10.15
Can I use my 2012 iMac For a monitor using a new Mac mini
iMac 27″, macOS 10.15
Yes.
See here: Use your iMac as a display with target display mode - Apple Support
Note that the resolution will be limited to what the iMac can display, so no 4K even though the Mac Mini can produce 4K resolutions.
Old iMac for a monitor