Thanks @ajlittoz . Yes you are correct, that is the source of the problem, the document came from .docx. However, it has so much formatting at this point, including many many inserted images, that pasting it as unformatted text into a blank .odt document and formatting from scratch would not be feasible.
What I did was open the original .docx document I wanted to convert from inside LibreOffice, and then saved it as .odt. This works many times better than saving the document as .odt from Word. LibreOffice has become leaps and bounds times better at both saving and reading and converting Microsoft formats in the past few years, very welcome improvements that have enabled me to move more and more to open document formats. Keep up the great interoperability work LibreOffice!
So the document is in great shape now in .odt format, using only styles, not direct formatting. And the few places where the conversion did not work well, on page styles, I easily fixed. Mainly by creating a Landscape page style and applying that to the “ConvertedX” landscape pages, and then applying the default page style to the portrait pages that followed the landscape pages.
The only issue left is cleaning the styles to get rid of unused ones. I am fairly sure the dozen or so remaining “ConvertX” page styles are unused. But the macro to delete unused styles did not delete the ones still there, so I am confused. If there is no way to search a document for where a page style is being used, I will have to just live with them remaining. Thanks again.