What are some alternatives?
When comparing Messenger Video Calls and Slack Video Calls, you can also consider the following products
WhatsApp - WhatsApp Messenger: More than 1 billion people in over 180 countries use WhatsApp to stay in touch with friends and family, anytime and anywhere.
Zoom - Zoom unifies cloud video conferencing, simple online meetings, group messaging, and a software-based conference room solution.
Daily.co for Intercom - Free video calls & screen shares embedded in Intercom
Confrere - Professional video calling. No downloads. Just a link.
Amazon Chime - Online meetings and video conferencing
mynameis - Ridiculously expensive video calls-on-demand