As described here I do not consider KDE5 ready for everyday use, as there are some important features missing as well as several bugs.
One of the things that annoyed me after installing Kubuntu 15.04, was the fact that gnome apps wouldn’t register to the system tray. But there is a solution ’till the KDE devs introduce a permanent fix…
A simple way is to install “trayer” from the repositories. This is a small and lightweight system tray. Then resize your KDE Panel, leaving some empty space at the right of your screen, which the trayer will occupy (in this example 200px). Start trayer giving the parameters that suit your needs, for example:
trayer --align right --widthtype pixel --width 200 --transparent true --heighttype pixel --height 30 --alpha 230 --padding 10
This will place the tray in the right side of your screen, having width 200px, height 30 px etc… Change the parameters depending on your preferences. Now, GTK apps will place their tray icons on trayer. You can get all possible options in the man page of trayer, by typing in your terminal:
After you experiment a bit with the trayer settings and conclude with what suits you, put it all on a script. You can then make it run on KDE login.