irc.rizon.net has some fairly active channels, among them #r9k.
irc.lainchan.org is active. It has #lainchan and #general, where people regularly talk
irc.euirc.net has a few active channels, but most of them are not in English. #lobby is English.
irc.libera.chat is active, albeit mostly for technical discussions. #thelounge exists, but I don't remember how active it was.
irc.2600.net and irc.scuttled.net respectively. They are mainly about computer hacking, linux and programming, but it's mostly chit-chat.