If a microphone is captured while sharing system audio, the system audio will be mixed with the local microphone and published.
Supported Browsers
Share System Audio only supports browsers based on Chromium version 74+, such as Chrome, Edge, Opera, and so on. Other browsers are not supported at this time, e.g. Safari, Firefox.
Chrome for Windows & Chrome OS supports sharing system audio + tab audio.
Chrome for MacOS & Linux only supports sharing the tab audio.