Install kde-config-gtk-style by entering the following commands in the terminal:
sudo apt update sudo apt install kde-config-gtk-style
Description:
KDE configuration module for GTK+ 2.x and GTK+ 3.x styles selection
Configuration dialog to adapt GTK+ applications appearance to your taste under KDE. Among its many features, it lets you: - Choose which theme is used for GTK+ 2.x and GTK+ 3.x applications. - Tweak some GTK+ applications behaviour. - Select what icon theme to use in GTK+ applications. - Select GTK+ applications default fonts. - Easily browse and install new GTK+ 2.x and GTK+ 3.x themes. . This package contains kde-gtk-config module for KDE System Settings and common files (icons, localization files and etc).
Homepage: https://projects.kde.org/projects/kde/workspace/kde-gtk-config
Version: 4:5.12.4-0ubuntu1
Section: universe/kde