Hello Karl, I am not involved in the packaging of phonon, but still a few questions.
Have you any Qt4 applications installed? Because src:phonon in version 4:4.10.3-2 was the last version that built the Qt4 parts. Since src:phonon 4:4.10.3-3 just the Qt5 packages get build anymore. And therefore I guess phonon and phonon-backend got replaced by phonon4qt5 and phonon4qt5-backend some time ago. Maybe there should exist a transitional package for upgrading phonon to phonon4qt5? Kind regards, Bernhard