The following is from u/jimoxf post on Reddit. The 'screen' command can be used to turn any Linux Box (e.g. Pi) into a Serial Console Server.

sudo apt get install screen

Run the following to find the serial devices available

ls /dev/tty*

Plugging in via USB Micro B, a Palo Alto Networks firewall showed up as ttyACM0 Running the following will) will get you to the console prompt

screen /dev/ttyACM0

I'm thinking how this could be combined with a celular modem in the Pi + a Secure Configuration + some remote management tool and this could easily be a handy 'out of band management' box a whole lot cheaper than other alternatives.

This blog post on the matter in a little more detail.

The original idea from Terry Henry's YouTube video.