Qt5ct
From wikinotes
Qt5 attempts to match settings from current desktop environment.
qt5ct lets you set deskto-environment agnostic overrides.
Documentation
man qt5ct
https://manpages.ubuntu.com/manpages/bionic/man1/qt5ct.1.html repo https://sourceforge.net/projects/qt5ct/
Locations
~/.config/qt5ct/qt5ct.conf
user config ~/.config/qt5ct/qss/*.qss
user qss stylesheets for UI /usr/share/qt5ct/qss/*.qss
installed qss stylesheets referenced in UI
Enable
export QT_QPA_PLATFORMTHEME=qt5ct