Have you tried the same with the online WEB IDE https://www.espruino.com/ide/
I am running Chrome App, v0.73.7 without any problems.
Uhhhh...this problem come from ubuntu permissions. Need to change serial port permissions i.e.
sudo chmod a+rw /dev/ttyUSB0
to enable serial port read and write.
Need to change serial port permissions
or add your user to dialout group
@Lackó started
Espruino is a JavaScript interpreter for low-power Microcontrollers. This site is both a support community for Espruino and a place to share what you are working on.
Have you tried the same with the online WEB IDE https://www.espruino.com/ide/
I am running Chrome App, v0.73.7 without any problems.