I have set the Numix theme as my GTK+ theme in Gnome Tweak Tool. This works for most programs, but the ones made with KDE don't care about it.
This is how every program should look:
This is how KDE based programs look (I tested Kmplot and Step.):
I don't know if this is the expected behavior from KDE programs or not, but Kmplot did use the Numix GTK theme before I switched to Ubuntu GNOME from Plain Ubuntu (both 16.04LTS and I used Gnome Shell with Plain Ubuntu too).
How can I make KDE programs use the specified GTK+ theme?
