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.
But now the illegal content is not happening on their owned instance, taking them off the hook.
Communication network providers in the EU generally aren’t liable for illegal activity of their users.
That doesn’t make it a non-issue. Ignoring the obvious ethical issues, there are still serious costs to addressing conduct they’re made aware of, both in terms of actual man hours and mental health of any employees, and the actual bandwidth of the abusive traffic.