My old Paperwhite is definitely a bit of a more enjoyable device to read on, but the portability of the X3 makes it amazing for carrying around in your pockets all day.

I have the Bluefox NX1 and would definitely recommend it if it's the right fit for you. It runs Android 15. I use it for a secondary alarm clock, offline maps, music player, and bulk storage of off the grid media like Wikipedia and book guides for whatever I can find.

Here it is next to the case for my S23 Ultra:

I can get more pictures later if you want.

I installed it after about a week. The stock software was serviceable, but it didn't have any support for text formatting (like bold text) which DCC uses extensively.

These ones have a pretty powerful magnet so you can attach it to your phone using the metal ring sticker that comes with the e-reader.

I prefer having it separate personally. A 3D printed case would be a cool alternative though.