I’ve got a kindle keyboard 3 and want to know if there’s anything better out now. My main requirement is being able to load in my own content and have a nice cover/case
I don’t care about apps or web browsers, but it would be nice to have something that is easy to sync or upload data to.
ONYX BOOX makes several different models, including some with color screens and most with reading light built in. They also have fantastic battery life. I have a Poke 2 which has lasted a month of active reading before needing to be charged.
These are basically Android tablets, so data transfer is not locked down. You can put whatever you want on it.
I know you said you don't care about apps, but on these you can run basically any Android app (within limits of e-ink screen functionality), including useful stuff like Obsidian for notes and Syncthing for syncing files across devices.
In hindsight, that's what I'd go for. You could have audiobookshelf, tachiyomi or any of your favorite android reading apps. But the Kindle does what it does well, and for relatively cheap. Maybe in 5 years I'll reconsider, if my kindle ever dies!
I just got a Boox Page to replace an early generation Kindle Paperwhite. Being able to load up android apps makes it much more useful (I find it to be great for cooking from recipes I store in Paprika) plus more flexibility with the eReader app you use.