What would you recommend a free software product for video conferencing (Video Conferencing)?

Question

Computer networks

Good afternoon!
Is there free software (or VERY inexpensive) for organizing video conferencing with the ability to connect up to 100-200 people? The main performance characteristics that are needed:
1. The possibility of creating and simultaneously holding several different videoconferencing with a different set of participants.
2. Possibility of displaying presentation materials (word, exel, powerpoint documents, photo, video)
3. Possibility of centralized interactive control of the meeting format:
a) 1 speaks and shows, others are not visible on the screen, but everyone sees and listens
b) 2-4 are displayed on the screen and actively communicate, others watch and listen.
It is desirable to have a built-in chat with the ability for all participants to write about problems with video / sound.
Expensive commercial solutions such as Polycom, E-works, we will not pull, the organization is budgetary. 20 thousand rubles - that's the maximum that I can count on. But if there are free analogues, they will be considered first of all.

Answer 1

I once used the big blue button: bigbluebutton.org

Answer 2

openmcu.ru + jabber

Answer 3

Can arrange freeswitch + free sip client.
But a server for 100-200 video calls will go beyond 20,000 rubles, not to mention the fact that even a free product must be able to configure

Answer 4

This thing was used for 10 people https://meet.jit.si/

Answer 5

Kurento is a free webrtc media server. The number of subscribers will depend on the power and channel width of the server on which it is installed.
For twenty it is quite possible to find someone who will install and configure it.
He will take care of your tasks.