To reproduce, run attached example and press the button. The text does not appear.

One line of text seems to work fine, but if there is more than one, problem starts.

Attached example reproduces it for Kubuntu 23.04 (2 lines). On Ubuntu 22.04 I can reproduce it if I put a little more text there so that it wraps to 3 lines, then it only renders the very first line.

What seems common in the two cases is that it prints binding loop error when this occurs.

qrc:/qt-project.org/imports/QtQuick/Dialogs/quickimpl/qml/MessageDialog.qml:12:1: QML MessageDialog: Binding loop detected for property "implicitHeight"
qrc:/qt-project.org/imports/QtQuick/Dialogs/quickimpl/qml/MessageDialog.qml:12:1: QML MessageDialog: Binding loop detected for property "implicitHeight"