On Firefox (multiple versions) the Dropdown for voice (recieve) device is "none" and always and only "none." Screenshot was done on Firefox 58.0.1 (Also tried on Firefox 50.1.0) Chrome is fine in this regard, although there were issues with "everybody hearing everybody." Upon connecting with Chrome, the GM and one other player could hear me, but I could hear all five other people. The people who could not hear me had to click the "reconnect" button in settings in order to hear me (and subsequently lost the ability to hear a different person). Eventually enough reconnecting allowed everyone to hear everyone. The GM had to use both Firefox and Chrome: Chrome for voice, but Chrome's graphics were messed up and so he used Firefox to see what he was doing.