Found:

turning a QLabel to render markdown text via .setTextFormat(QtCore.Qt.MarkdownText) and using a linebreak like <br> hides ALL text after the linebreak.

Expected:

the label makes an immediate linebreak like it does with QtCore.Qt.RichText and line in the example PySide6\examples\webenginewidgets\markdowneditor and

context

One can even increase the hight of the label like shown in the attached demo. It just looks like there is no more text.

additionally: The double space-method does not work either! See wikipedia But it does not end up removing the text.