I wrote a videoconference BigBlueButton plugin.
BBB is an opensource videoconference system with a number of great features (including api), oriented on online teaching but quite suitable for seminars and conferences, too.
The plugin code is available here: https://github.com/vasylOstrovskyi/vc_bbb
Features already done: creating and configuring rooms, starting and joining sessions, pre-uploading presentation files, managing recordings (view, delete).
Any feedback is welcome (sorry for not perfect code, I am not a programmer).