https://banglejs.com/apps/ says web bluetooth is disabled on firefox (the browser I am using).
The quick start guide says that it is disabled current on my laptop.
Getting started with espruino cli and the following output is observed.
$ espruino --list
Espruino Command-line Tool 0.1.40
-----------------------------------
PORTS:
/dev/tty.debug-console (undefined)
/dev/tty.wlan-debug (undefined)
/dev/tty.Bluetooth-Incoming-Port (undefined)
zsh: abort espruino --list