It seems like Hoopla does a lot of self-published and indie published books. That kind of fits in with their business model where they charge a flat fee per lending of the book, so they have an incentive to get as many books on the platform as possible.
This is a group that gets independent author ebooks into public libraries. Perhaps contact them to find out how to do it:
https://indieauthorproject.com/authors/
It seems like Hoopla does a lot of self-published and indie published books. That kind of fits in with their business model where they charge a flat fee per lending of the book, so they have an incentive to get as many books on the platform as possible.