2021 Mac mini use iPhones for camera?

Hi, driveinauto....it's possible, what you're mentioning is called "Continuity Camera".....here's a link to the Mac requirements:

Continuity Camera: Use your iPhone or iPad to scan documents or take a picture on your Mac - Apple Support (CA)

and here's for the iPhone end of things:Continuity Camera: Use iPhone as a webcam for Mac - Apple Support (CA)

you'll also need Ventura on your Mac, so you'll need a Mac capable of running that..... the other requirements for it should be in the 2nd link I included in my answer to you

[hope this helps]

john B