[Quoth]

Do a version from a wordprocessor for ebook (extra save as docx if not editing on docx, which you shouldn't for LO Writer), then when proofed change the styles, index, footers, headers, page numbers, foot & end notes and syntax highlight (via character styles) for direct export as PDF. Automatic epub to pdf is only a convenience feature.

But I was last writing C++ docs in 1987 and C++ has changed a bit since then and also better authoring/format tools.

Don't use markdown or pandoc. Markdown is for very basic input for a draft version using a plane text editor. I abandoned it years ago.

Also zero direct formatting (glass typewriter syndrome), use styles for everything.