Since there seems to be an increasing demand for an IRC client on Genode I ported irssi. You can find it in my (cnuke) index under Tools (Extra), available for arm_v8a and x86_64.
The port uses goa¹ and pretty much all of the more advanced stuff — modules/plugins and so on — is disabled or untested, like DCC. The pkg contains the ISRG Root X1 certificate, so verified TLS with servers using letsencrypt certificates should work (libera and OFTC are the networks tested so far).
Irssi will create its configuration directory .irssi in the file-system labelled with home, where you can make all the usual adjustments.
The port was not thoroughly tested yet but basic functionality appears to work fine — I visited our IRC channel #genode at irc.libera.chat:6697 successfully today.
Edit: published a arm_v8a pkg as well.
¹) I am using a somewhat modified version at the moment so you might not be able to built it yourself.