Since this is available as a separate plugin, it would be up to someone to package it separately for Debian.
- Bug#793130: pidgin: No system tray icon on KDE Plasma 5 Diederik de Haas
- Bug#793130: pidgin: No system tray icon on KDE Plasm... Diederik de Haas
- Bug#793130: pidgin: No system tray icon on KDE P... Ari Pollak