7.0.0b2 just reverts a change that broke ADE ePub decryption. All the following still applies!
Here is an early version of the DeDRM plugin for calibre 5.x.
There will be bugs. It won't work for everything. It needs a lot more testing and bug fixes.
But I think that it might work for Kindle for PC/Mac (non-KFX, non-Topaz, non-print replica) and downloaded for transfer vis USB to an e-ink Kindle (again, non-Topaz, non-print replica).
I think it also works on Adobe Digital Editions (ePubs) with ADE 2.0.1.
I think this includes finding Kindle for PC/Mac and ADE keys.
But much more testing is needed. It might not even work for the items listed above. But I think it is a starting place.