Can't delete it, so I'll just share what I did in case someone needs it in the future:
- Go to Settings > Privacy & Security
- Under Cookies & Site Data, click on Manage Exceptions button
- Start pasting the websites that MS Teams requires, but remove the "[*]", as FireFox/FireDragon does not accept it.
- Click on Save Changes
- Restart the browser to be sure
*Tested Working 12-July-2021 9:20 PM GMT+8