[exaltedwombat]

Try. In Sibelius, Export/Graphics/SVG. Add the resulting SVG files to the Images folder in a new Sigil document. Create sufficient blank pages, Insert a SVG file into the Body area of each (working in Code View, of course). Put in enough metadata (Title, language..) to keep the validators happy. Add a Cover.

See if the result works in ADE. Drop it into Kindle Previewer and see how the conversion pans out.

There's more.... You've still got the fonts issue to sort out (even if some of the formats display OK on YOUR computer, which has the Sibelius fonts installed). But start learning!