since using kvantum, the font list in scribus is scrambled. I've checked other programs font listing using kvantum and have not come across any issue like this. Something for the developers to look into.
got an update to add, inkscape has a similar issue.
see this thread:
https://inkscape.org/forums/questions/rows-of-fonts-on-text-and-fonts-list-is-illegible-on-4k-display/
Very recently, Nitramr fixed a bug related to the fonts list display:
https://bugs.scribus.net/view.php?id=17514