Now it depends against new version. Old code can be removed

kstyle/breezestyle.cpp

@@ -226,11 +226,7 @@ namespace Breeze
             QStringLiteral( "org.kde.KWin" ),
             QStringLiteral( "reloadConfig" ), this, SLOT(configurationChanged()));
 
-        #if QT_VERSION < 0x050D00 // Check if Qt version < 5.13
-        this->addEventFilter(qApp);
-        #else
         connect(qApp, &QApplication::paletteChanged, this, &Style::configurationChanged);
-        #endif
         // call the slot directly; this initial call will set up things that also
         // need to be reset when the system palette changes
         loadConfiguration();