You need to install a 3rd party software Blackhole to even get desktop audio for screen recording with QuickTime. After about an hour of troubleshooting settings I gave up and used OBS, esp since I was in a public space at the time and the Blackhole config disabled my headphones and for a moment you could hear a loud YouTube tutorial playing through my Mac speakers. Also the shortcut to stop screen recording on QuickTime sucks, it’s like CMD+CTRL+ESC and you need to have it memorized because there’s no “Stop Recording” button option