My Linux user group used to hangout in IRC until 3 or 4 years ago when little by little we stopped joining the channel. Some of us tried IRC clients for smartphone and it was a lousy experience.
Until one day someone created a Telegram group. Now we are all there, the conversation might not be as fluid as IRC, each is in their own timezone, but it is there.
Scrappy founder here. Telegram crushes it for low latency, instantly synched desktop/mobile flexibility, easy topic channels and groups, and trivial bot API. I've not seen anything do what it does as perfomantly.
For code, wiki, and issues, it's self hosted Gitea. It's a dream to fire up thanks to Go and SQLite, and users forget you're not at GitHub.
Nothing more than those two plus email needed here, yet anyway.
Yes, IRC I think finally "failed" once persistence went from "nice to have" to "need to have" feature. Yes, you can work around this if you are a top 20% techie who enjoys that stuff, but most don't.
Mobile basically made the "all clients synced from anywhere" a necessity, and then lack of IRC client development for things like rich media hurt to boot.
Until one day someone created a Telegram group. Now we are all there, the conversation might not be as fluid as IRC, each is in their own timezone, but it is there.