If you want to screenshare and play audio from an external app, you may notice that you're not hearing audio. This is normal when sharing from a browser, but there are some easy solutions:
Voicemeeter for PC
Download the application, play video and audio through your PowerPoint Presentation or from another application on your device.
Loopback for Macs
Download the application, play video and audio through your PowerPoint Presentation or from another application on your device.
RTMP Streaming
This is available on the Main Stage and within Sessions.