The short version of what and how (AFAIK):
1. Any Amazon ebook that can be loaded onto a eink Kindle running firmware earlier than 5.18.5 can be transferred from that Kindle to Calibre, and--using plugins--DRMed and converted to other formats. Note that a few ebooks can not be downloaded to an eink Kindle. (The Amazon entry for the book will tell you)
2. Any Amazon ebook with a "publication date" earlier than April 22, 2025 can be downloaded on a Windows PC using Kindle for PC 2.4 and then transferred to Calibre and DeDRMed and converted using the same plug-ins.
3. Any ebook can be loaded on Windows Kindle for PC 2.8 and then DeDRMed using a
complex and slow method