When you run arduino-cli board list, your board doesn't show up. Possible causes:
- Your board is a cheaper clone, or
- It mounts a USB2Serial converter like FT232 or CH340: these chips always report the same USB VID/PID to the operating system, so the only thing we know is that the board mounts that specific USB2Serial chip, but we don’t know which board that chip is on.
For a deeper understanding of how FQBN works, you should understand the Arduino platform specification.