Best Opensource Software from an Admin perspective so far is: https://www.discourse.org/ - administrating it is basically either click two buttons or from time to time ssh / ./launcher app rebuild .. that's it. It has been running stable for over a year and is so freaking smooth…
Discourse - Civilized DiscussionOne platform. Any community.Discourse is the customizable, scalable community platform powering more than 22,000 communities that create knowledge through conversation.