Other platforms I’ve used… for myself or for clients. Smashwords, draft to digital, Lulu, Ingram Spark. I’ve yet to use Kobo and Nook (Barnes & Noble) Each one is different on how you upload and set up your book to some degree. Most of them do wide distribution which means you can still get books on Amazon, however, the royalty is peanuts. During these Covid times, I don’t publish paperbacks on KDP due to not being able to get Author Copies sent to NZ. I have to use Lulu instead. I don’t like the paperbacks on Draft to digital (unless they have changed since I last looked.) I like Smashwords because it means those who use a screen reader can still download and read your book. It really is a matter of picking and choosing what is right for you.