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plznot IMO it's best to do as much as possible in LO. If you learn how to use its template and style features you will have less fiddling and editing to do after any conversions, see ==>>
Libre Office: Using Styles and Templates.
Using Styles rather than inline styling will also result in
much neater code in the conversion output. And, I recommend saving as DOCX and converting that. The DOCX input module does a better job than its ODT equivalent, and its actively maintained by Kovid Goyal (calibre creator/owner).
BR