As it turns out, if you have one of the new Mac mini, you can use an iPad Pro as a screenshot with Astropad's Luna Display dongle, designed to switch an iPad to a second screen for a Mac.
Luna Display has not previously been used as a primary display because it has been paired with Macs equipped with a screen, but since the Mac mini has no display, it is the perfect machine for testing a iPad Pro as a primary screen.
In a blog post, Astropad explains how the Luna Display dongle iPad app and Mac app can be used to turn iPad Pro to a Mac mini display, with full instruction available.
According to the Astropad team, using iPad Pro this road was like a brand new product because it is essentially macOS on iPad with the Luna app and a regular iPad Pro when it's not in the Luna app
This setup combines the best of both Mac and iPad with the power of the Mac Mini and the edge of the edge of the corner of iPad ]. Using Luna, we can take full advantage of all the pixels on iPad at full retina resolution. It provides several ways to interact with MacOS, where you can seamlessly flow from mouse, keyboard, to Apple pencil, to interactions. And since Luna is running over WiFi, you have the flexibility of an entire wireless work area. Everything only works.
To get the same setup, you need a Luna Display dongle to connect to Mac mini s USB C port, associated apps, a iPad Pro (some will work but the best results will be seen with Apple's latest model), a keyboard, a mouse, and a reliable WiFi network.
Luna Display can be purchased from the Luna Display website for $ 80.