Zulip?
The concept that every message belongs to a topic and the async communication focus makes so much sense to me. I read conversations, not timelines.
It is highly ranked on some platforms that do validated reviews, like Capterra.
(I lead the Zulip project).
We're planning to roll it out at our company (foundata) in Q4, so you’ll get at least a few bucks from us. I'll also happily recommend it to our customers. As an OSS company and service provider, I can very much relate to the lack of marketing budget and the constant SEO spam.
If I had to say it would have to be something customizable, letting a user to delete their data even after getting kicked from a server, very fast and seamless joining process ,great gif/sticker support without any premium features etc. But really that's just some fantasy app lol. Discord is doing just fine destroying itself however
By the way, I didn't know there was an instant online test app because when I searched for Zulip I was in the download page and it doesn't say anything about trying it online. Seems like a strange suggestion UX wise but that's how I feel about it (wonder how many people missed out on this?), same thing after you enter the app. It should have a test area for the new user to chat around by himself with a bot or something with locally/session stored messages.
https://github.com/zulip/docker-zulip
https://github.com/zulip/docker-zulip/blob/main/compose.yaml