Alternatives to big-name proprietary remote-lecturing tools As in many other universities, due to the coronavirus outbreak now we are supposed to do our teaching online in videoconference style. Our university suggests using either Microsoft Teams or Google Meet, but I am not so keen on using a service run by one of these data-collecting behemoths where "you are the product".

Which alternatives exist to these two big players for videoconferencing with a large number of students?

For my lectures, I would like to share my desktop's content (livestream) and my voice on microphone. Students should hopefully also have a way to give feedback and ask questions. You may assume ca. 100-200 students.

My university used to have an internal videoconferencing service but they discontinued it.

I would prefer something open source, in theory: I understand that bandwidth does not grow on trees, but that seems like a problem that could be solved using p2p, at least in theory. Otherwise, I am open to considering other commercial services that are a bit more privacy-preserving; for instance, something run by a company less focused on advertising and monetizing user data. Apple looks slightly better, and so does Amazon (Twitch -- it has ads, but I don't know how intrusive they are).

In the past I used to publish my in-class lecture videos, but I realize that by doing so without a class I would lose all interactivity.
BigBlueButton is software designed for remote teaching. It makes it possible to teach using videos, share slides, annotate them, do breakout rooms, etc., and can be integrated with Moodle. It is open-source and can be self-hosted.

It is apparently not easy to set up, but can be done, and can scale to dozens of participants provided they don't all have their webcam set up (e.g., only the instructor and a few people asking questions share the webcam).