While searching for ways to create a private intranet for my author friends and I to utilize, one option I looked at was VanillaForums. It has some great options out of the box, with the ability to create groups of interconnected forums, subforums, and discussion boards based on topics. The ability to add reactions and to include files and photos in our posts was also a big draw. I loved that as it has an open source option, I could host it myself and save a lot of money, as we are starting with only a few users.
Unfortunately, a lot of extras are add-ons for Vanilla. To fully customize your site, a knowledge of CSS and HTML is almost mandatory, as there aren't really any options for simple customization like adding color codes to a pre-built theme or uploading a background to the same theme.
When bugs are posted about in the Vanilla forums, they aren't handled very quickly. I understand that a lot of times most bugs are user error or add-on related so every circumstance is different, but when it is a bug in the system itself, then it's not the user's responsibility to 'you break it, you fix it' as stated on the open source documentation.
For users who are used to the forum-style architecture, Vanilla is a robust software that provides some great add-on options and is pretty user friendly on the front-end. For me, I'm used to PHP based software that was a full social network, so I found the forum/discussion board options limiting and it didn't suit my needs. However, I we need a forum option in the future, Vanilla will likely be my first pick.