One can also remove DRM from books one purchased with Calibre+DeDRM plugin.[0],[1],[2]

[0]: https://www.reddit.com/r/Calibre/comments/1c2ryfz/2024_guide...

[1]: https://www.mobileread.com/forums/showthread.php?t=361503

[2]: https://forum.linuxconfig.org/t/calibre-and-dedrm-problems/8...