IRC stands for Internet Relay Chat and was one of the first instant messaging protocols. Many say it has been superseded by other protocols and platforms but some make very good arguments for why it's still very useful. Personally, I prefer it to pretty much every IM app or platform I've tried.
- If your client doesn't support TLS, I recommend looking into Stunnel
The "official" channels are
#nixnet-ot. As the names suggest, the first should be used for anything related to NixNet and the latter for anything off-topic. Rules are few but check the Terms of Service for specifics.
This server runs oragono and comes with a lot of nice features baked-in, such as NickServ, ChanServ, message history (disabled by default), and multi-client support. The docs are a mixture of information pertaining to admins and users; ignore the admin content and focus on what might be pertinent to users.
If you would like a web client, I host TheLounge at irc.nixnet.services. If you'd like a TUI, there are some great clients in the delightful-cli list. I personally use WeeChat. For graphical client, HexChat is a popular option, as is Pidgin.