How do I route audio from Phonon applications to JACK?

Phonon is a “thin” layer used by many KDE applications to play and record audio. It actually doesn’t contain any implementation itself, but instead uses another software library to get stuff done. The most common backend for this is GStreamer, and so to get Phonon to route audio via JACK you should generally just follow the instructions for GStreamer. If you use Phonon with the Xine backend instead of GStreamer, there’s no information for you here yet.