On the right side of the jPC is a USB-C port. This port is a USB-to-Serial interface that can be used to view very early logs, and, once booted, can be used as terminal to run commands from.
When a PC is connect to the jPC via this port, a USB-to-serial port will be enumerated on the PC. Use a terminal emulator on the PC (e.g. Putty, Tera Term, etc.), to open a connection to the serial port to interact with the jPC.
With just a PC (e.g. a notebook) and a USB-C cable, this port can be used to administer and troubleshoot the jPC both at development time, and when deployed in the field.