I don't think I've been on IRC since 2006ish. It was the gathering ground for my favorite private torrent tracker at the time. We had internet radio and all kinds of fun stuff.
Before that, like back in the AOL days, there were chat-based filesharing server rooms, where you would get a list of files, then request whatever illicit goods you wanted via chat commands.
I'm not really sure what people use IRC for now, but it's still active.
I've heard Matrix is closer to Discord, but not quite as feature-rich - with the tradeoff being open source. I joined the Matrix room for Jerboa development just to follow along, and then my home Matrix instance has a chat it threw me in when first logging into Element that I let roll but mostly ignore. I have no idea what I'm doing or even why I really joined, other than to check it out for myself to see what it's all about.