If you're looking for cross platform, Rocket.chat[0] has face to face conferencing in browser via WebRTC, although you do have to setup your own server [0]: ht

If you're looking for cross platform, Rocket.chat[0] has face to face conferencing in browser via WebRTC, although you do have to setup your own server [0]: https://github.com/RocketChat/Rocket.Chat https://github.com/RocketChat/Rocket.Chat