Well, for quassel, there's also a mobile app. On the Play Store the beta version is quite neat, and the F-Droid version. The normal Play Store version is from 2013, though.

I - maintainer of QuasselDroid - am currently working on a next version, though, which will take another few months.

For iOS, though, quassel-webserver is the best you'll be able to get, and it's quite meh on mobile.