On Linux, use picocom:
picocom /dev/ttyUSB0 -b115200
and press enter to get a REPL (or press the RESET button on the board if that does not work).
You should now see the
>>>
prompt.
Don’t have picocom installed?
sudo apt -y install picocom
Got permission denied errors?
sudo usermod -a -G dialout $USER
then logout and log back in or reboot!