I've yet to run into an Amazon-purchased book that Calibre can't liberate, and I haven't even updated Calibre since installing it a few years back. Where are you seeing this turn up? If I need to be looking for alternate sellers or finding some workaround, better to know it ahead of time, I suppose.
As the parent post said, the only way right now to "crack" is to dodge it. To have Amazon send you a copy of your book for a older device or older version of the PC software that doesn't support KFX, so they have to send you a crackable format instead.
I haven't done anything with Barnes & Noble in quite some time, but I've been curious to try a eBook purchase from there to see if their current DRM is any more friendly.
As mentioned just up thread, if you don't purchase in the most recent KFX DRM format, you can strip the DRM. However AFAIK this is illegal to do for Kindle Unlimited ebooks. You are not supposed to keep them, just borrow.
