No way to enable QPlatformTheme::HoverEffect in GUI

[q234rty]

QPlatformTheme::HoverEffect is defined in https://invent.kde.org/qt/qt/qtbase/-/blob/6.6.1/src/gui/kernel/qplatformtheme.h#L264-L274.

According to https://invent.kde.org/qt/qt/qtbase/-/blob/6.6.1/src/gui/kernel/qstylehints.cpp?ref_type=heads#L501-L517 and https://invent.kde.org/qt/qt/qtbase/-/blob/dev/src/gui/platform/unix/qgenericunixthemes.cpp#L503-L504, this should be enabled by default on desktop platforms.

However, qt6ct provides no interface to enable this and the current only way is to delete the line starting with gui_effects in the config file, to force a fallback on QGenericUnixTheme::themeHint(QPlatformTheme::UiEffects). That is however reset whenever one apply settings through the GUI.