terminal-wise, irssi and weechat are the traditional ones recommended these days. but there's a couple newer ones like catgirl: https://git.causal.agency/catgirl/about/ and some rust ones out there.

GUI-wise there's HexChat, mIRC, Quassel, lots of interesting options to look at.

May be worth digging through these tables a bit more if you're interested: https://ircv3.net/software/clients