Because I am hellaciously lazy and did not want to have to bother with an Apple account in spite of having a Mac laptop, I sell on Apple through D2D. Well a month or so ago I got an email that I could apply for an Apple promotion of Historical Fiction first in series. (This was the first such email I'd received, so I'm not sure if it is a new thing or I just hadn't received any) So I applied and one of my novels got in. To my surprise, it has done fairly well. Not Bookbub level well, but more than 100 books sold (reduced price not free) and some sell-through of books 2 and 3. The sell-through on Amazon is always better than on Apple because Apple doesn't make the books in a series clear the way Amazon does.
One advantage of going direct with Apple would be that I could put a link to the next book at the end which D2D does not do. I must admit Apple doing promotions is news to me. Does anyone know if they offer them to people who list directly with them? I list directly with Kobo in order to use their promotions which give me so-so results, not great but worth being in.