After the first few times I had apple remove a book from my library, and the only explanation they ever gave me was "sometimes books change, and when books change they are a new book," I just went back to DRM free. If I have to jump through hoops, and still can't keep the content I legally purchased, why would I legally purchase the content?
I believe it was Sea of Sorrows for me. The first time I contacted them asking what was up, since I wanted to read the book I had purchased earlier that year. They "gave" it to me as a "one time exception."
I never purchased a digital book again. Though I did still contact them again later that year, asking why it was gone yet again.
They tried to give me a "this may be an updated version" and I was like "no, this is a fucking novel based on a video game, they aren't releasing new versions every few months like textbooks."
True. But 1984 is still pretty strong, memory holes, double think, denying reality. Fascist organizations dictating what people can know, say, think, remember.
That's very much on the nose. But regardless, huge massive red flag, you don't own something that you have in your library unless it's physical and can't be removed at a whim.
Honestly, I havent bought a digital book since. You can read between the lines there.
I don't actually believe there will be a place to purchase DRM free books. Most of the ones I am seeing from a cursory search are for copyright free books.
kobo.com sells books without DRM (under eBook details they tell you the exact format). For example, the murderbot chronicles are sold without. Sadly they don't have everything like amazon does, especially for niche authors that only publish digitally.