-
ensure that
glib2,dconfandxdg-desktop-portal-gtkare all installednote: these package names apply to Arch;
glib2anddconfprovide thegsettingsanddconfbinaries and dbus interfaces, respectively. -
add the following overrides (e.g. for "All Applications" in Flatseal) to fix theming for X11 GTK apps:
--filesystem=~/.icons:ro