You essentially made them run on xorg instead of wayland.
The only common QT application that I know of that has an open bug regarding this is smplayer.
In fact I have QT_QPA_PLATFORM="wayland;xcb" in my /etc/environment so the opposite is applied system-wide (and okular opens fine).
But if its a gnome thing then its a gnome thing. 
Does not change the fact that the package you have installed is not in the repos. It might have used to have been. In any case you should not need it any longer.