I have come to the conclusion after reading internet posts concerning Scribus that it is not yet ready for prime time and having been in development for 20(?) years now, most likely never will be. It still can't even do footnotes? And the very first instructional step in the documentation, written by the developers, is wrong, and causes a crash?!!! AND, the current stable version cannot run on the current Mac OS, at all?! I had to fight all the way with LibreOffice to write my last book, but it did at least get the job done.
I wish the Scribus developers well, but this seems to be a dead issue.
Thanks for trying to help.