So what's everyone's favourite forum software? Which of the many packages out there would actually be suitable to replicate the usability of Slack/Discord, without making all of the messages disappear like in a black hole?
1) Discourse: https://www.discourse.org/
Looks pretty modern and also offers managed instances if you'd like, but i can't help but to feel that it's pretty JS heavy and there is perhaps too much whitespace, which makes navigating longer threads somewhat cumbersome. To me, it seems like a case of UI > UX, which is an upsetting trend that i've noticed ("make something pretty rather than something functional").
2) Flarum: https://flarum.org/
This one is perhaps a bit better in my eyes as far as the UX is concerned and seems to have actually been developed as a mobile first forum. It does have that modern look while at the same time being reasonably functional, and the idea of putting the forum structure tree in the sidebar actually works pretty well!
3) phpBB: https://www.phpbb.com/
Personally, this is my favourite from the "traditional" forum software, since it's really usable, it keeps a good information density, doesn't lose usability and isn't as JS heavy as any of the other alternatives. Also, there are plenty of plugins and even the default functionality provides you with most of the things that you'd like in a piece of forum software and the hardware requirements are pretty low.
As someone who runs a phpBB forum or two myself, the biggest pain is perhaps updating, since you run into the very same issue of never knowing whether an update will break something or not and you might have to manually alter some config files if things go sideways. Also, admittedly, the admin UX could be better, but i guess that's just the software showing its age.
That said, old is not necessarily always worse.
4) Simple Machines Forum: https://www.simplemachines.org/
To me, it looks like a slightly simpler alternative to phpBB, with similarly good readability, slightly lower information density, but overall a very similar look and feel to phpBB. Can't talk much about its features, but some people have recommended it in the past.
Also, in regards to the free plan memory limitations, has anyone here experimented with self-hosted IM solutions? Personally i'm running a Rocket.Chat (https://rocket.chat/) instance which seems pretty nice and functional, for example, for a smaller software developer team, though others also have had good experiences with Mattermost (https://mattermost.com/) or other software.