Profanity is a command-line ncurses based XMPP (Jabber) client. It's easy to use and seem inspired from irssi for the interface. It's available on OpenBSD as a package named "profanity".
It's really easy to use and the documentation on its website is really clear. It supports all main XMPP features including OMEMO / OTR / GPG for end-to-end encryption.
To log-in, just type **/connect myusername@mydomain** and after the password prompt, you will be connected. Easy.