Same with the Barnes and Noble Nooks. I've never rooted one, but via ADB one can install a launcher and most Android applications run. I've used four generations of Nooks to run AnkiDroid.

Just beware to check what version of Android the Nook is using before you buy, and what your app needs.

Android on an e-reader unlocks so much potential. I've owned four or five Kindles over the years but recently switched to an Onyx Boox page 7" as my main e-reader. Expensive (relative to Kindles) but runs full Android 11 and has physical page turn buttons. I use an app called BookFusion to sync my library including reading position across all platforms. Battery life isn't Kindle grade but I can get by charging once a week which is a good enough tradeoff for the convenience of being able to run Android apps.