The first thing I did with my kindle that I got 10 years ago was to turn on Airplane mode and never turned it off since. I can upload books there via usb just fine, and I never had an issue.

If the device was not locked they wouldn’t need to support it.

If the device was able to read epub it would require pretty much minimal support.

Amazon chose to make it hard to support their own products.

switched to kobo when bezos gave $100 million to drumpf. the old kindle still sitting in bottom drawer. might become a doorstop soon.