Would like to hear your suggestion of an alternative that:

* has a modern interface and allow people to communicate efficiently

* does not cost a fortune to use

* has good moderation tools

* supports multiple channels

* has enough built-in moderation so that spam/illegal content is minimal

etc.

Zulip. Open source, self-hostable, looks decent and not only does it have every feature that discord has, their version of threads/topics to spin off individual conversations is extremely well done.

Zulip?