It seems that the effect of calling QWidget::setAttribute(Qt::WA_OutsideWSRange) on Wayland has changed recently, but I'm not sure what the correct behavior is.

I noticed this issue while investigating this bug report for Konqueror. Konqueror uses a QWebEngineView to generate thumbnails of html files: to avoid showing the view, it calls QWidget::setAttribute(Qt::WA_OutsideWSRange) on it. However, at least with Qt 6.8.2 and Wayland 1.23.1, this doesn't work anymore and the view is shown.

In a virtual machine with Qt 6.8.0 and Wayland 1.23.0, this doesn't happen and the QWebEngineView isn't shown.

I attach a program showing the issue: it has a button to show a new toplevel widget and a check box to decide whether to call QWidget::setAttribute(Qt::WA_OutsideWSRange) on this new widget before showing it. With Qt 6.8.2 and Wayland 1.23.1, the widget is visible regardless of the state of the check box; in the virtual machine with Qt 6.8.0 and Wayland 1.23.0 the widget is visible only if QWidget::setAttribute(Qt::WA_OutsideWSRange) is not called.