To be able to choose the theme Qt applications are using on your Linux system, tweak some settings, and have an overall better integration with Gnome / Gtk, you can give Kvantum a try. This is a SVG-based theme engine for both Qt4 and Qt5, KDE and LXQt. Using it, you'll not only be able to theme Qt4 and Qt5 software to match your current Gtk theme almost entirely (as long as your current Gtk theme has a Kvantum theme available), but also configure some Qt theme-related settings.
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