Sidecar vs Luna vs Duet

I have a 11” iPad Pro and 2018 Mac mini.

I want to use my iPad as a monitor for my Mac mini occasionally BUT not at as a second monitor, but as the only monitor.

From reading it seems side car only duplicates or extends if I have a monitor plugged in already.

Duet also seems that way.

It seems Luna is the only one that can stand alone as making the iPad the monitor itself.

Can anyone confirm?