Integrate Teams with Zoom.US
Zoom is an excellent replacement for WebEx, maybe even the best right now. Slack allows us to force Zoom.us to be configured as the audio call, video call and screen sharing interface.
Zoom.us is fast to launch, so it makes it ideal for audio calls, video calls and screensharing.
I'd suggest Teams allow admins to config to force use of calls with Zoom.
PS. WebEx VP Engineering started a company called Zoom, and it's really good (and inexpensive too).