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.
There’s plenty of disposable email services out there.
And they’re added to spam lists all the time. All you need do is draw up a list of the twenty most popular, because frankly Gmail and outlook already cover so many while leaving room for privacy-friendly providers.