How to enable focus effect (as in QLineEdit) for QAbstractScrollArea subclasses?

[Stefan Scherfke]

In Qt5 (and KDE), QAbstractScrollArea subclasses (like QTextEdit or QListWidget) don't highlight their frame when they are focused (unlike, e.g., QTextEdit, which gets a nice blue border when it has the focus):

How can I enable a similar effect for QTextEdit/QListWidget/...?

I already tried various variantions of frameStyles and I don't think that using setStyleSheet() should be used for such a common problem.?