If you and your friends chip, it’ll be a few bucks a pop per month to have your own private server with voice chat rooms and video chat rooms.
It’s all opensource and contributes to the ecosystem. Best of all, no age verification because the data is yours.
Actually I did just ask the same thing, and the TL;DR is that most clients do handle it as signal with group chat folders. Cinny does look like Discord, but currently lacks voice calling. It’s currently web only with PWA support for mobile, though.