I found a list of monitors that support 4K and 120Hz with a Mac mini M1. It can be found here by scrolling down to Mac mini (M1, 2020):
https://tonsky.me/blog...The HDMI output only seems to support HDMI 2.0, which only supports 4K 60Hz. Only HDMI 2.1 supports 4K 120Hz.
So a Thunderbolt output with USB-C connector comes into question for the video signal. The connection cable must of course support the high frequency of the video signal, which unfortunately is not apparent from a connection cable.
The soon to be available Caldigit Thunderbolt 4 Dock (
https://www.caldigit.com/thunderbol...) supports 4K up to 144Hz on the Mac mini M1. (I'm also ordering one as soon as it's available here).