kde-plasma-smooth-tasks as currently shipped in Fedora 22 and Rawhide depends on the Plasma 4 kde-workspace. Therefore, it does not work under the version of the KDE Plasma Desktop workspace shipped with Fedora 22 and higher, which is Plasma 5. (In fact, it does not even install, due to broken dependencies. But even if we were to ship the missing libraries, it would still not work.)

If a Plasma 5 / KDE Frameworks 5 / Qt 5 port exists upstream, please upgrade the package to that version as soon as possible. If not, your best course of action is to retire the non-working package from Fedora 22 and Rawhide as soon as possible (now that it is still possible to retire Fedora 22 packages). (Porting Plasma widgets (plasmoids) from Plasma 4 to Plasma 5 is a significant amount of work and thus not something easily doable downstream. In particular, the user interface now MUST be written in QML 2.) The package can be resurrected once it gets ported upstream.

Thank you for your cooperation.