No but recently Amazon also pushed an update to make this happen, so people who got this update cannot locally upload books on their devices anymore and have to use Amazon services to buy and download books. Luckily for older devices jailbreak is still an option. Also, people who didn’t update can still use Calibre too apparently. Customization is far better with jailbreak anyway though.
It was impossible to upload books to these devices except for through Amazon?
No but recently Amazon also pushed an update to make this happen, so people who got this update cannot locally upload books on their devices anymore and have to use Amazon services to buy and download books. Luckily for older devices jailbreak is still an option. Also, people who didn’t update can still use Calibre too apparently. Customization is far better with jailbreak anyway though.