Had the same issue on Arch Linux. Manually replacing hicolor directory with oxygen worked for kate but resulted issues at other apps. Finally this resolved the whole problem: http://www.webupd8.org/2015/11/configure-qt5-application-style-icons.html
Had the same issue on Arch Linux. Manually replacing hicolor directory with oxygen worked for kate but resulted issues at other apps. Finally this resolved the whole problem: http:// www.webupd8. org/2015/ 11/configure- qt5-application -style- icons.html