https://www.bbc.co.uk/news/articles/c98k91yy4z4o
"The move will mean owners of older Kindles, including its earliest models such as the Kindle Touch and some Kindle Fire tablets, will be unable to download new e-books."
For a more tech-oriented site, according to Ars Technica Amazon removed the ability to upload over USB:
https://arstechnica.com/gadgets/2026/04/starting-in-may-pre-...
"Previously, owners of old Kindles could have worked around this loss of functionality by downloading books locally and transferring them via USB. But Amazon removed the ability to download books to a PC or Mac in February of 2025."
I don't like to brag "I told you so" but I saw this coming 16 years ago: