With Fedora 39 dropping adwaita-qt for its Qt5 and Qt6, the issues with Qt's built-in theme are showing up. 

In particular, when using dark theme, certain widgets (push button, tab widget, scroll area) are reverting to bright theme when they are inactive (the window is out of focus) or disabled. 

Upstream bug: https://bugreports.qt.io/browse/QTBUG-112879

The upstream has a series of commits to address this issue, slated for the upcoming Qt 6.5.4 and 6.6.1 releases. So for qt6-qtbase, this will sort itself out once Fedora updates to the new release.

But for the qt5-qtbase, the following commits should be backported on top of already-backported theming support carried by Fedora qt5-qbase build:
* Fix memory leak in QGtk3Interface::themeName - 55d3a2442c92addd688a9f570515d391a79bf2cf
* Fix disabled button color in Linux (X11/Wayland) - 3e971798e73d5414f65841f70de0ba5d5f71097f
* Fix inactive palette in gtk3 theme - 18a8b8f3c6d6bff6d646599572c59b09e97e34b0
* Fix tooltip palette issue in gtk3 theme - 173038ae190f36866070181a6cb5b5f743c33539
* QGtk3Theme: define light, midlight, mid, dark and shadow colors - 516cae81dfc82c7289445c34389aa6bf0de2d79f

Reproducible: Always

Steps to Reproduce:
1.Run a Qt5 application that does not provide its own theming overrides (such as VirtualBox, or Qt Widgets Gallery Example from Qt for Python)
2.Drag the window around or bring a different application window to focus.
Actual Results:  
The affected widgets switch to bright theme.

Expected Results:  
All widgets should retain dark theming.