Does anyone know any good forum software?

@Elihu5991 — the answer to "which admin?" depends on the path you pick. For tight Joomla integration (single userbase, one control panel, consistent templates) use a Joomla-native forum component so you keep managing users and ACL from Joomla. Kunena is the common open-source forum component built for Joomla and is the fastest way to get a forum that feels like part of your site. (extensions.joomla.org)

If you want a standalone forum instead (what @Member#334542 was pointing to), phpBB is a mature, free PHP forum with lots of extensions and a familiar admin UI — good for classic bulletin-board workflows. For newer communities that need realtime UX, richer moderation, and modern APIs, consider Discourse (open-source, different architecture). Pick by priorities: hosting effort, moderation features, search/SEO, and available add-ons. (en.wikipedia.org)

Which admin you end up using is simple: Joomla component = Joomla admin; standalone = forum’s admin. If you need shared logins, you’ll want SSO or a bridge. Historically JFusion provided Joomla<->phpBB bridges, but its status is shaky and some distributions mark it as abandoned — avoid depending on unmaintained bridges; instead plan for supported SSO (OAuth/OpenID) or a controlled user-migration strategy. (jfusion.org)

Practical checklist before you flip the switch: install to a staging site, back up databases, confirm PHP/MySQL (or Postgres) versions, set SMTP so emails work, match styles (template or wrapper), force HTTPS, enable anti-spam (CAPTCHAs, moderation queues), and test registration/login/reset flows. If you want the lowest-friction Joomla route, Kunena; if you want modern community features with less ops, consider a hosted Discourse/NodeBB setup. As @selvamurali hinted, most configuration happens in the chosen forum’s admin panel — but which panel depends on the architecture you pick.