True, one person needs an account. You used to be able to do Jitsi - and before it other webrtc calling solutions - with no account at all but now Jitsi also needs the first host to sign in.

But Signal calls, every participant must have a Signal account. The others, I can invite people to join with no account.

“Browser tech”? Just the fact you can make it work from a browser without needing to install anything else. Again, Signal isn’t set up for that kind of thing. It’s just designed and extended from a different use case.

Jitsi. Even zoom and teams allow joining without an account. Good ol’ webrtc and browser tech.