Fired up the old mIRC license I've had for decades last week to explore old servers and channels. Many are dormant, but life is still teeming in many. I'll probably wind up re-donating to mIRC developers and investing some time into IRC communities. I find the experience preferable to Discord.
Anyone interested in exploring this segment of the internet, start with: https://netsplit.de/
Netsplit is a great and vital resource. But I'm wondering if it's actually the best entrypoint for people who just wanna chat with others about some topic. https://libera.chat/ seems a bit more user-friendly and "hand-holding", for the people who prefer that. If Libera doesn't fit their vibe, the huge network list on Netsplit will surely be of more use to them once they understand IRC just a tiny bit better.