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.

If you prefer not to self-host Jitsi and be identifiable via your domain, there’s jami.net as a replacement for Jitsi. It is a decentralized conference app that requires you to install an app. However, it’s open-source and account creation is optional. It’s available for all major platforms (Mac, Windows, Linux, iOS, Android), including on F-Droid.