Breeze Dark theme installed but not detected by systemsettings5

English Applications
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Leap 15.4: gtk2-metatheme-breeze, gtk3-metatheme-breeze and metatheme-breeze-common packages are installed, but systemsettings5 shows a “Breeze” item only; there is no “Breeze Dark” item. On Leap 15.3 both items are available.
If I select “Breeze”, the result is a mixture of dark and light GTK apps; more precisely, GTK3 apps have dark colors and GTK2 apps have light colors.
I have read that KDE Plasma developers are dropping the Breeze support for old GTK apps, but strangely, Adwaita theme works perfectly, even with Filezilla, which is based on wxWidgets; in that case, systemsettings5 shows the two items “Adwaita” and “Adwaita Dark”.
Any idea?

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You can try the options in Qt5 Settings
Run

qt5ct
3

No changes. It seems that Qt5 Settings does not affect the style of GTK apps.