With a few others, I struggled through setting up a "distributed" (i.e. not all on a single machine) BBB deployment early in the pandemic, back when the documentation and community explosion hadn't quite happened. Such a deployment is nonstandard and you're left to your own devices to make it work, albeit with some decent architectural documentation so that you can work out which component needs to run where.
BBB does rely on WebRTC exclusively for its media. The so-called 'HTML5' client is in-browser. There is a Flash-based client that's officially deprecated, and they're slowly stripping out support for it.
There is also some optional Etherpad integration, so that you can collaborate on in-meeting notes that are made available afterwards.
BBB's biggest problem right now is that the Debian packaging, which is the only official way of deploying the software, is not open source. It's also really messy -- some stuff goes into /usr/local, some into /opt, with a fair deal of leftover crud that isn't used any more like the Flash client.
This is an unintentional situation, but the maintainers have deprioritised making the software truly "open source" (IMO) in favour of bugfixes and features.
I don't think this situation meets the GPL it's licensed under, regardless of whether you would qualify this as "open source" or not.