Recently I have converted one of my iCloud notes into an EPUB by first copying and pasting its content to Pages (by parts, since the entire content was not willing to be copied for some reason), then by manually designating all the headers as Pages headers (to get the table of contents working), and then by using the Pages "Export to EPUB" option. This was a lengthy and unpleasant procedure. Is there a better way to turn a note into an EPUB? By the way, I specifically need to have all the images from the note in the resulting EPUB document.
Sorry you had challenges with the copy to pages. In my experience, the content from the note to Pages is generally excellent and one step. Pages has EPUB export capabilities and it will take over all function for authoring from iBooks Author in the next OS release cycle in 2020.
I think you will find the hassle to get it into pages lessened over time and benefit from having it in a format you can edit easier than PDF.
You can save a Note as a PDF in the Notes App. Then you can use EPubIr to convert the PDF to EPUB. EPubIR is an app available at the link above. It sells for $2.99.