gmenudbusmenuproxy creates ~/.gtkrc-2.0 on startup, which makes kconf_update not write the default theme. As this is a race condition, as a result some installations have the correct GTK2 theme set and some don't.
Git commit ff84a4e5662ee7058073af34ead9645d63562bb1 by Fabian Vogt. Committed on 16/10/2019 at 06:57. Pushed by fvogt into branch 'Plasma/5.17'. [gmenu-dbusmenu-proxy] Don't create ~/.gtkrc-2.0 Summary: BUG: 412970 Test Plan: GTK-2.0 applications use breeze again. Global menu activation still works. Reviewers: broulik Reviewed By: broulik Subscribers: plasma-devel Tags: #plasma Differential Revision: https://phabricator.kde.org/D24664 M +8 -2 gmenu-dbusmenu-proxy/menuproxy.cpp https://commits.kde.org/plasma-workspace/ff84a4e5662ee7058073af34ead9645d63562bb1