ndeed, you missed:
https://lists.fedoraproject.org/pipermail/devel/2014-March/196343.html
libappindicator is now (since Fedora 22) also REQUIRED for GTK+ system tray
applets to work under KDE Plasma. (Plasma 5 no longer supports the legacy
XEmbed-based system tray protocol that the builtin GTK+ classes implement.)
Please DO NOT REMOVE libappindicator support from your packages. Instead,
actually ADD it where upstream supports it and it is not yet enabled in
Fedora.