@alex_malyu Very helpful post, thanks!

Solution: Controller.prototype.IntroductionPageCallback = function() { // Installer is "updater" when it is run with "--updater" // or Controller does "installer.setUpdater()" if (installer.isUpdater()) { var widget = gui.currentPageWidget(); // Same as gui.pageById(QInstaller.Introduction); widget.findChild("UpdaterRadioButton").checked = true; // Disable paint events on these widgets, through the QWidget::updatesEnabled property. // I tried with the "visible" property, but it is not enough, because for some reason // that property gets reset under some conditions. For example, if "Next" button is pressed // and no updates are available. widget.findChild("PackageManagerRadioButton").updatesEnabled = false; widget.findChild("UninstallerRadioButton").updatesEnabled = false; } }