While Jitsi is open-source, most people use the platform they provide, meet.jit.si, for immediate conference calls. They have now introduced a “Know Your Customer” policy and require at least one of the attendees to log in with a Facebook, Github (Microsoft), or Google account.
One option to avoid this is to self-host, but then you’ll be identifiable via your domain and have to maintain a server.
As a true alternative to Jitsi, there’s jami.net. It is a decentralized conference app, free open-source, and account creation is optional. It’s available for all major platforms (Mac, Windows, Linux, iOS, Android), including on F-Droid.
People were doing illegal stuffs on it
Possibly stupid question: if they found out that people were doing illegal stuff on it, doesn’t that mean that they were monitoring people’s conferences? I thought that the FOSS community was big on privacy.
I imagine they’re receiving reports from other parties, such as law enforcement, that there are inappropriate things happening, rather than monitoring the streams themselves.
No, because we don’t know how they got the information. Someone might as well just have reported it, or it was forwarded from law enforcement.
Théry are plenty of FOSS people who don’t believe in privacy. Just because you like openness in one thing doesn’t mean you want it in another. Though there is probably a larger overlap.
I get what you are saying, but the Venn diagram is basically overlapping circles. Yes, they are not exactly the same thing, but you would be hard-pressed to find somebody who advocates for/regularly uses open-source software yet isn’t as passionate about privacy. It is reasonable to assume one who advocates for one is also advocating for the other. 
That’s just not true at all. You’re talking from a very small circle if you think most OSS is used by privacy buffs. The largest users of OSS are companies, followed by techies who enjoy the challenge or the ownership. Privacy wonks are by far the smallest userbase.
I did not say people who use it. I said people who advocate for and regularly use OSS. Plenty of people use open source software because it is the most popular or it is what was recommended to them. Obviously that group exists in large number.
What kind of illegal stuff?
starting video chat with one self, with nobody else involved