Are there any eBook readers one can use in freedom?

[J.B. Nicholson]

I would like to try reading some DRM-free eBooks with a backlit eBook reader which is 
lighter than using a laptop and less expensively than using a laptop.

I don't need it to be network accessible (no wifi, no Bluetooth needed) so long as it 
has a USB port and a high capacity storage medium (perhaps a compact flash card) that 
I can easily copy eBooks to, install in the eBook reader, and use the eBook reader to 
read files.

File format support should include common eBook formats that one can use in freedom 
(I'd imagine PDFs and epub are reasonable choices).

The device should offer the ability to be recharged, ideally with batteries I can 
replace. It's also okay if the device needs to be plugged in while using the device.

It's fine if the device has no upgradable software on it so long as what's on the 
device works reliably. Editing and/or marking up what I'm reading is not required.

Does anyone know of a recommendable device that would do these things?

I looked in https://ryf.fsf.org/ and https://h-node.org/hardware/catalogue/en and I 
didn't notice anything named "ebook reader" or similar language. If I've overlooked 
something I should consider, please do let me know the URL for that device.

Thanks.