While it's not DRM free... DeDRM [0] can be run stand alone or as a plug-in to Calibre. I have it auto run when I import a new book to my collection. From there you can do what you like with it.
You need to download the books from the "Manage Your Content and Devices" page using the "Download & transfer via USB" link. Those still use the old DRM.
Baen [1] is another to mind that imprint-wide believes that DRM is a waste of time. As another poster pointed out it is interesting that it is mostly sci-fi imprints leading the vanguard of DRM free, in terms of well known commercial publishers.
You can only do this on the minority of drm unencumbered books and even then the UI for simply getting at that drm unencumbered file is a complete mess especially if you are buying and trying to read the book on an actual computer.
[0]: https://github.com/apprenticeharper/DeDRM_tools