[CarbyAu]

I second Jitsi. For me, the value is in hosting your own Jitsi server. Really not that hard to do.

Mind you, I only host it at home on a VM for personal use. Have had sessions with 6 people with one of them a Europe-Australia connection. All fine on default 720p.

If I were looking for 20+ meeting software though I'd consider something else. I would consider it a case for streaming to faceless attendees. I have never had a meeting with useful input from more than 10 people.