Can a 27" Imac be used as a monitor for Mac Mini

I am thinking about buying the new Mac Mini M2. I already have 2 27" iMacs which are in good working order. One of then is a 2013 Model and no longer supported by Apple (running on Catalina). If at all possible I would love to use this Mac as my main screen for the Mac Mini. I contacted support and they said this wasn't possible. However I have been told that there are work arounds. Any opinions or advice would be welcome. However my tech level is Amoeba minus, so please speak in plain talk <LOL>