When using a physical keyboard on iOS and activating Full Keyboard Access (Settings/Accessibility/Keyboards & Typing) accessible elements are partially supported. The implementation of accessibilityFrame and accessibilityActivate in QMacAccessibilityElement seems to be used by Full Keyboard Access, as navigating and activating items on screen works. But the QMacAccessibilityElement does not react to focus events.

By reacting to the UIFocus didUpdateFocusInContext signal and making every accessible element focusable to the UIFocus API with canBecomeFocused the QAccessibleActionInterface::setFocusAction() can be succesfully triggered.