gregstoll·há 2 meses·discussHopefully it will just work, if not please file a bug! I tested with a variety of hardware and sites but of course I couldn't try everything...
gregstoll·há 2 meses·discussYup! Arduino is one of the things I tested with. (I worked on this for Mozilla)
gregstoll·há 2 meses·discuss(I submitted a PR for caniuse a few days ago :-) https://github.com/Fyrd/caniuse/pull/7523 )
gregstoll·há 2 meses·discussAs others have said, you'll get a dialog if any site actually tries to use this. But if you want to fully turn it off, just set "dom.webserial.enabled" to false in about:config (and restart Firefox)