

Modern BBSes aren’t an issue – they’re out there, and they’re pretty good these days – but the lack of VC funding that lets them fund massive user growth isn’t there, so the level of friction re: setting up your own remains high.
Discord’s advantage is that it’s not just easy to set up, but also free. You’re not going to get that in the forum space anymore. ProBoards isn’t going to invest the money into making them sexy anytime soon.
It works the same on Lemmy, it’s just that on Lemmy you subscribe to groups, and on Mastodon you subscribe to users.
Groups just forward replies and other interactions it sees to subscribers.