I use The Lounge, it's a self hosted server/bouncer that you use through a web UI. That makes it so I can stay online 24/7, and can access IRC from any device including my phone. It even supports push notifications, so when someone pings me on IRC, I get notified on my phone and can go open up the client and look at my chats. It's pretty good!
Not as lightweight as a terminal client, but keeping a Firefox tab open for it isn't that memory hungry. Negligible when you have dozens of tabs open and a few Electron apps anyway.