https://bugreports.qt.io/browse/QTBUG-135158
https://codereview.qt-project.org/c/qt/qtdeclarative/+/647212
--- a/src/quicktemplates/qquickpopuppositioner.cpp
+++ b/src/quicktemplates/qquickpopuppositioner.cpp
@@ -321,5 +321,8 @@
                                                  : p->parentItem->mapToGlobal(windowPos.x(), windowPos.y());
     QRectF rect = { globalCoords.x(), globalCoords.y(), popupItem->width(), popupItem->height() };
-    if (!skipFittingStep) {
+
+    // QTBUG-99618: On wayland, we can't use QWindow::mapToGlobal(), and should use a xdg_positioner instead.
+    static bool isWayland = QGuiApplication::platformName().startsWith(QLatin1String("wayland"));
+    if (!skipFittingStep && !isWayland) {
         const QScreen *screenAtPopupPosition = QGuiApplication::screenAt(globalCoords.toPoint());
         const QScreen *screen = screenAtPopupPosition ? screenAtPopupPosition : QGuiApplication::primaryScreen();