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.
Harper.