Free teams alternative for a webinar?

cross-posted from: https://lemdro.id/post/43110258

There's a nonprofit that wants to do several meetings for lectures for about 3000 students. The presenter will show screen or share a document for the most part. At the end students would raise hand and have some discussion, so they will be just viewers for most of meeting

Of course, big corps like teams and google meeting won't Handel this much, not for free at least.

Could I suggest jitsi to them? Can it Handel this much? How much is it going to cost?