@rl_dane has written a very good blog post on books. He lays out the categories of physical books, ebooks, and "librebooks." Librebooks are ebooks with no DRM.

https://rldane.space/paper-books-vs-e-books-vs-librebooks.html

It's sad that DRM-free ebooks are enough of a novelty to be their own category.

I think he makes a good point about loading "librebooks" onto an ereader "varies in complexity." Programs like Calibre do require readers to play the librarian.