My old method was to use Apprentice Alf’s DRM removal tools running under the older rev of Kindle app. Procedure was to download books in old kindle app, I had a Hazel job watching the kindle folder and copying the various book format files into a convert folder and a Calibre process to automatically run the items in the convert folder through de-DRM and bring them into my Calibre library. Not to steal or hurt any authors but because I want a free and usable copy of the books I buy.
Old revs of kindle app don’t work on Catalina and the new file formats are all DRMed even from publishers who have said no to that outdated technology.
I tried the suggested new replacements: Download from the web to an old kindle device using the feature to transfer by USB to get an older .AZW format file. Updated the de-drm plugins in Calibre to the latest versions but they still won’t remove the DRM.
I found references to some tools from a company called Epubor but not to sure about them and want some info from other users first.
Or any other suggestions.