chatto

https://github.com/chattocorp/chatto
https://chatto.run/

I deployed this to one of my own servers, and saved the deployment scripts here: https://github.com/llimllib/chatto-install

it's run great, very easy to install and hasn't caused any hiccups at all in light usage

https://bsky.app/profile/hmans.dev/post/3mehazd6c4c2u
https://www.hmans.dev/blog/chatto-timeline

Somebody else had the same idea as me, to build a slack/discord clone.

He has an instance available, but seems similarly in dev as I am

update: chatto is now open-source (AGPL) and self-hostable

Meanwhile, I have done zero work on my own similar idea. Kudos to the author!