tried one more reboot to be sure. won't launch.
Scribus crashes due to Signal #11
QWidget::repaint: Recursive repaint detected
QPainter::begin: Paint device returned engine == 0, type: 2
Segmentation fault (core dumped)
I've seen this qt/kde stuff as the basis of a few non-launches at the scribus bug page. Which, in case anyone is wondering, is not romantic reading on a Thursday evening.
I'm removing Solus' version and reinstalling the Flatpak. Not solved in any way, but the flatpak works. No harm no foul as they say.