@Willbo Phone
Presenteers would connect to a Jitsi Meet instance, where a volunteer (Room Monitor) would also connect to receive the presenter's audio/video and communicate with them. The Room Monitor would introduce the presenter to the live stream audience and use gstreamer to share their screen to the Icecast streaming server. Viewers would connect to Icecast (HTTP[S]) to get the stream. The stream was in video/webm format (vp8 yuv420p 1280x720, vorbis 44100 Hz mono). The website Live page included a viewer for each of the three room streams, and a IRC widget (KiwiIRC). There was an IRC channel for each of the three rooms, and an IRC channel for the whole conference, and one for tech support. IRC channels were on Freenode.

Additionally, the FSF held their annual associate membership meeting, as was usually done during LibrePlanet, this time via Mumble instead of in-person. Also using IRC and Etherpad. There were at least 26 people in the Mumble room at the same time. It worked well.

Scripts from last year:
https://libreplanet.org/wiki/LibrePlanet:Conference/2019/Streaming
Setup from 2017:
https://www.fsf.org/blogs/sysadmin/free-software-video-streaming-hubangl-powered-libreplanet-2017

Some limitations of the streaming setup (which they were working on but ran out of time) were:
Viewers disconnected when the input to Icecast changes.
No lower-bandwith alternative stream for viewers.
The Jitsi Meet server did not have presenter mode, so most people could only show either their slides or their face, not both.