As of 13th July, 2022:
The latest version of the tools is 10.0.3 from noDRM for calibre 6.x and 5.x (Python 3). It should also work with calibre 4.x and 3.x (Python 2).
Details are at
https://github.com/noDRM/DeDRM_tools
If you have any problems with this version, ask at
https://github.com/noDRM/DeDRM_tools/discussions, NOT here at MobileRead.
Spoiler:
The tools were originally written by many people, and were maintained by Apprentice Alf and Apprentice Harper until November 2021.
The latest version of the tools from the Apprentices is 7.2.1 for calibre 5.x
Details are at
Apprentice Alf's blog and
Apprentice Harper's github repository.
If you have any problems with this version, you should probably start using the version from noDRM