I'm a cli junkie but I've gone from using very minimal tiling WMs to vanilla Gnome. So I've stopped using bitlbee for example, but bitlbee is something I'd use a lot in the days of 100% terminal.

It's an IRC proxy for other protocols like Skype or Slack.

I have no idea how it stands up today but I always liked the concept of having one service that handled conversion of all the modern protocols to text based.

Other than that I think people have already given amazing recommendations so I have nothing to add.

I also used to use bitlbee, but once AIM died I dropped it.

Slack dropped their irc gateway a while ago. I recommend wee-slack[1] which is a weechat[2] python plugin that uses the Slack API instead of the old IRC gateway, which also means it is a lot more feature rich than the IRC gateway was.

1 - https://github.com/wee-slack/wee-slack 2 - https://weechat.org/