LimeChat. LimeChat is an open-source IRC client. It's fast and lightweight, and it has a console-like interface
http://limechat.net/mac/
Colloquy
Downloaded from phone or computer app center
Textual. Textual is a native Mac IRC client, so it takes full advantage of macOS features like the Notification Center.
Downloaded from App centre on phone or mac
Weechatirc app
https://weechat.org/