The videoconference technology, Zoom, is really good for large numbers of people. You just have to have access to a laptop or computer with a webcam and microphone.

thanks for the tip x3 but that is exactly the trouble. where i teach, lot of students barely have a decent internet connection, forced to the limit now that everybody are using it even lot more than usual

and some others simply must use their cellphones to work, so i must mantain it so simple as possible

You better not use zoom. This has been hacked too often and behaves like a malware.
Meanwhile SpaceX and NASA have banned its use. In addition, the FBI is investigating Zoom.

Unfortunately, hackers managed to spy on the users via Zoom, which is also due to the really miserable security architecture of Zoom.

Some alternatives suggested by my university are:
PEXIP
Webex Teams
Webex Meetings
MS Teams

You can also use Discord which also runs very stable.

I'm sorry if there are a few mistakes in there. English is unfortunately not my mother language.

Translated with https://www.DeepL.com/Translator (free version)

My university uses Zoom. We must just be really low budget then.

Other programs are:
DFNconf Adobe Connect
DFNconf PEXIP

But they only work for universities, and Adobe Connect is poor at noise cancelling.

sorry for the delay to respond X3 yeah, just after i saw your message appeared lot of news about Zoom XD but my work decided to use classroom, not me, so i am safe. Just google can control all my movements XD