One problem when people ask this is that my favorite channels are mode +s (secret, not on the public list or revealed when you whois someone and see what channels they're in) with a dozen or fewer active participants (but often 20-50 total members or more) and inviting new people would risk killing the vibe we have going in there. I found these channels basically by word of mouth or friends of friends. While it might sound like gatekeeping, I think everyone should probably find their own way, based on their interests and network. I will say I tend to hang out on Rizon, though.

I do also idle in a lot of the tech channels in Libera, but that's not where I spend most of my time chatting, I'm basically just in those for tech support. I like to already be in the ones for the programs/distros I use so I can read the last bit of conversation before (and after) posting. Both in case someone else had my problem recently, and because it gives me something to do while I wait, like reading a magazine in a lobby. Sometimes the tech support even goes both ways and I'll chime in on an old convo if I think I can help someone.

If an IRC channel gets too busy it'll be hard to have conversations in also, like the madness you see in Twitch chats with the text scrolling by rapidly.

I’ve found the IRCs hosted by tilde servers to be quite good. See https://tilde.chat/ and https://tildeverse.org/. I’m a member of https://ctrl-c.club (although I haven’t been active for several years).