If you're ok with introducing a little bit of latency, the easiest way forward is webrtc to rtmp conversion. You could easily introduce headless mixing capability on top of https://github.com/voc/voctomix . We hacked together a quick and really dirty web frontend in https://github.com/FOSDEM/infrastructure/tree/master/ansible . It does the job, so we never felt the urge to change it...
Scaling the stream to ∞ viewers is easy using only free and open source software.
Feel free to get in touch.
How do you get 100k+ people on a stream without having to have massive bandwidth? Where is the stream actually hosted?
sorry if I'm asking basic questions.
Scaling live interaction with really large numbers of participants is problematic both technically and socially. My research hasn't really yielded anything that can reliably scale beyond ~50 users using only free and open source software.
[0] https://golightstream.com/studio/
[1] https://www.youtube.com/playlist?list=PLVGEH-HLZ76olPRIBvbjH...
Edit: Seems like they have a monetization plan now, and it seems reasonably priced compared to other services I looked at like livestream.com