https://www.cnet.com/how-to/record-your-computers-screen-with-audio-on-a-mac/
- Download Soundflower 2.0b2 (https://github.com/mattingalls/Soundflower/releases/tag/2.0b2) for Catalina
- Install Soundflower
- Reboot
- System Preferences > Sound > Output > Soundflower (2ch)
- Open QuickTime Player
- File > New Screen Recording
- Options > Soundflower (2ch)
- Record
- File > New Screen Recording