Gen Z here, most of my online life is on IRC. Learned about its existence a couple years ago. It is very much alive, although most people left there are at least semi-technical, and I miss the non-technical crowd.

I don't know, it was a very long time ago. Maybe do a search, based on your interests?

Slashnet still exists and it's fairly active depending on the channel. #xkcd was bumping last time I checked my client.

Libera is quite active