2019 Mac monitor compatibility with new Mac mini 6

Apple only sold one standalone monitor in 2019 – the 32" 6K Pro Display XDR. That monitor went for $4999+ USD and so it seems unlikely that it is the monitor to which you are referring.

If you are referring to an all-in-one computer – an

• iMac (Retina 4K, 21.5-inch-2019) or
• iMac (Retina 5K, 27-inch, 2019)

the 2019 iMacs are not monitors, and you cannot use them as hardware monitors for any current Macintosh.

Target Display Mode went away when the first 27" 5K Retina iMac came out in Late 2014. Apple also added restrictions such that no Mac released after 2019, or running anything later than Catalina, supports the use of any iMac (even an old one) as a Target Display.

There are workarounds that might let you use a 2019 iMac as a second display with significant drawbacks, but you will need at least one real hardware monitor or TV set for that new M6 Mac mini.

If you're referring to the 2019 Pro Display XDR then as Phil124 pointed out probably yes.

If you're referring to a 2019 iMac the answer is a definite no. Apple discontinued Target View Mode several years ago.

The are numerous excellent 4K monitors in 27" and 32" size for up to $500 5K monitors start at about $800. I got my LG 32" 4K monitor for $331.

Very likely yes, assuming you mean a Mac Mini with the M6 CPU.

How you connect it will depend which monitor it is exactly and what ports it has, but likely for a 2019 model, your looking at thunderbolt if its a Pro Display XDR. Just use a high quality thunderbolt 3/4/5 cable and plug it into one of the thunderbolt ports on the Mac Mini.

click here ➜ Plug in Pro Display XDR - Apple Support

and here ➜ Connect displays to your Mac - Apple Support