"Share system audio" in a Teams meeting has disappeared

On a Mac you can achieve this using audio extensions like Blackhole or Soundflower (now supports MacOS Catalina). Both are free and open source but there are paid for alternatives out there too.

An basic example of how this can work:
1. Install Soundflower
2. Set Soundflower (2ch) as your system sound output device in MacOS sound preferences (the app your using to play video will now send it’s sound to Soundflower instead of your normal system speakers).
3. In Teams you go to settings, set Soundflower as your Mic and then share your screen and play the video (everyone will see your video through the screen share and hear it via Soundflower).

One issue is you won’t hear the audio yourself. That can be fixed using MIDI setting on the Mac as follows:

1. Open the Audio MIDI Setup app on your Mac.
2. Create a Multi-Output Device by clicking on the plus sign in the bottom left of the screen
3. Select your system speakers from the tick list on the right (do this first)
4. Select Soundflower (2ch) from the same list
5. Check the Drift Correction option for Soundflower (2ch)
6. Rename your multi-output device if you want.

Now set your system to play audio to this multi-output device. In your MS Teams settings keep your speakers as your systems speakers (don’t use the multi-output device otherwise you’ll generate echos) and set your mic as Soundflower (2ch). Everyone on the call will now hear your systems sounds, including the sounds from the video when you play it. You will also hear the system sounds though your own speakers.

Don’t forget to switch your mic back to your real mic when you want to speak again.

https://github.com/ExistentialAudio/BlackHole
https://github.com/mattingalls/Soundflower

Well that's a creative way to "solve" things. Better KPI for the team? Not better for Mac users.

Vote and comment at the uservoice page, it might get some more attention then.