My own novel, The Immortal Remains, is DRM-free on Amazon, Kobo, Barnes & Noble, Google, and other platforms (maybe Apple as well, I'm not sure). Other authors, such as Cory Doctorow, sell their books DRM-free as well.

The uncertainty is part of the problem. Funny that even authors are not sure :)

I can't tell on https://www.amazon.com/Immortal-Remains-Lee-Hauser-ebook/dp/... that it's DRM-free. Amazon loses money in the small this way, but probably considers it more important to train people to not care.