The Kindle Paperwhite is great. I think the Oasis gets even dimmer, but you’ll need to pay a premium for it. Personally, I prefer to stay away from Amazon e-readers now that there are other good options available, though.

If you don’t want to be locked into the Kindle ecosystem, the Kobo Libra 2 is a good option. It lets you set the warmth of the front light, lights the screen very evenly, and even supports dark mode for ebooks.

I really like the Onyx Boox line myself (though my experience is admittedly limited - I’ve only used the Note Air 3C), but their full Google Play store support might be a negative for you, if you don’t trust yourself to not install social media apps. My experience is that having apps for Hoopla, Libby, Kindle, Kobo, Nook, etc., all on the device is a huge improvement to my experience.

The Onyx Boox e-readers are also a bit more expensive than alternatives - the cheapest e-reader by them that I would recommend is the Poke5 at 180 USD and the one I personally want is the Page at $250. (There’s also an in-between model, the Leaf2, at $200, that looks solid.) Of course, if you want a phone-sized e-reader, the Onyx Boox Palma is the only good option that I know of. Unfortunately, it’s also $280.

All that said, is there a comfortable place outside your bedroom (or at least outside your bed) that you can read? It’s technically better if you don’t read in the same place that you sleep (though reading on an e-reader in bed is still gonna be better than being on your phone late at night).