How to connect to a Prusa Mk3S via USB in Terminal on MacOS?

After connecting the printer via a USB C -> USB adapter, run:

ls /dev/cu*

In my instance the USB adapter was /dev/cu.usbmodem14101

Then run:

screen /dev/cu.usbmodem14101 115200

Where 115200 is the baud rate.

Et voila, you can see what the printer is doing.