Kunena is described as 'is the ideal forum extension for Joomla. It's free, fully integrated, and no bridges or hacks are required' and is an app in the Social & Communications category. There are more than 25 alternatives to Kunena for a variety of platforms, including Self-Hosted solutions, Online / Web-based, Linux, Windows and Mac. The best alternative is Discourse. It's not free, so if you're looking for a free alternative, you could try Flarum or phpBB. Other great apps like Kunena are Simple Machines Forum (Free, Open Source), MyBB (Free, Open Source), NodeBB (Freemium, Open Source) and FluxBB (Free, Open Source).
Discourse is an open source discussion platform built for the next decade of the Internet. A modern forum, everything's been redesigned to be easy. Self-hosted Discourse software is free, hosting service is paid.
Flarum is free, open-source forum software with a focus on simplicity. You can use Flarum to easily set up a discussion forum for your website. Flarum is developed openly on GitHub. It is the combined successor of esoTalk and FluxBB. It aims to be:
Since its creation in 2000, phpBB™ has become the most widely used Open Source forum solution. Like its predecessors, phpBB™ 3.2 “Rhea” has an easy to use administration panel and a user friendly installation process, which allows you to have a forum set up in minutes.