IRC channels are one of the most significant parts of Ubuntu community infrastructure. However, all Ubuntu channels I've ever met are hosted on irc.freenode.net. What's the point of irc.ubuntu.com? I've seen some users claiming they can be found there... But is that server used at all?
irc.freenode.com and irc.ubuntu.com refer to the same collection of irc servers. They are both CNAMEs (DNS aliases) for chat.freenode.net. The current setup is as following
As given on Ubuntu IRC channels
There are several Internet relay chat (IRC) channels on the freenode network (irc.freenode.net) used for Ubuntu support and development.
The best place to start for general help with Ubuntu or just to meet other Ubuntu users is #ubuntu or one of the many local language channels.
Specific channels are available for Ubuntu derivatives: #kubuntu, #edubuntu, #lubuntu and #xubuntu and separate channels relate to development, bugs, local community (LoCo) teams, accessibility and documentation. Choose from the current list of channels .
hope that helps.