To insure that kde-gtk-config works correctly (themes apply without restart and also to flatpak apps), the daemon "xsettingsd" most be running.
Git commit b6e7c6f056740e936adc94b7a843f6448f6830ab by Mikhail Zolotukhin. Committed on 10/03/2020 at 16:35. Pushed by gikari into branch 'Plasma/5.18'. [GTK Config] Add XSettingsd as a runtime dependency GTK Config Module uses XSettingsd to apply settings to GTK applications on the fly, thus making it an optional runtime dependency. To provide this information to distributions this patch is made. FIXED-IN: 5.19 M +7 -0 CMakeLists.txt A +32 -0 cmake/modules/FindXSettingsd.cmake https://commits.kde.org/kde-gtk-config/b6e7c6f056740e936adc94b7a843f6448f6830ab