That leaves v1.21 as the "sweet spot", but most of the sites that used to host that installer EXE have mysteriously disappeared.
It's like saying you can break BluRay DRM by recording the screen with your phone camera.
The other part is that there isn't a single definitive KFX file for a title. If you have an Oasis and I have a Paperwhite and we both download the same book, I believe we get different KFX files. There's no reason to doubt that there will be future Kindle devices that are even better with respect to typography and so you will need to re-download your library for that device.
Today, KFX can sometimes be De-DRM'd but it's gotten to the point where it's a cat and mouse game. It works for a while then Amazon changes something and breaks it. I don't doubt that essentially uncrackable DRM is achievable.
The real fix is legislative.
A search engine that covers all the little sites selling DRM-free books would be nice!
(Publishers of Norwegian books fortunately tend to have just do watermarks, which is fine – you can read the book on whatever device you want, and your copy has a little note saying "ex libris Your Name" or something)
[1] https://www.kobo.com/ [2] https://play.google.com/store/books
http://libgen.gs/ (NEW – November 2020)
http://libgen.rs – (NEW – October 2020).
https://libgen.is – (Working Again – May 2021).
http://libgen.st – (Re-directs to www.libgen.rs).
http://libgen.io/ (No longer working).
https://libgen.be/ (NEW – September 2020 – Search proxies to www.libgen.rs).
https://libgen.nl/ (NEW – September 2020 – Search proxies to www.libgen.rs).
If you are having trouble reaching with above Libgen URLs, try http://93.174.95.27 or http://185.39.10.101.