New M4 Mac Mini monitor equivalent?

There are literally dozens of monitors that would work. Without knowing anything about your criteria - size, resolution, color accuracy, etc. - it's difficult to offer any specific suggestions. You can start by looking at the reviews on a site like rtings.com.

Regards.

As mentioned, most any aftermarket display will work with the Mac mini.

see > Connect a display to Mac mini - Apple Support

never had a monitor not work with any mac I've owned, newest monitor I gotten is an 27" lg monitor it was pretty cheap only 1440p though and not OLED which is likely the reason it was cheap

LG 27” 5k is $500 less than Apple Studio display.