It’s not for me. My wife wants to read some manga and I think one of the apps she uses is only on android and other only on App Store. She currently reads on the web but it’s a poor experience according to her.
IMO, it depends on your OpSec, use case and budget.
Being here you are pro privacy and you are able to buy a high end secure device, hence, the decision is easy:
https://remarkable.com/products/remarkable-2
While primarily a note taking device, it can display PDFs and EPUBs. It runs Linux and has strong privacy features, though it's not dedicated to reading.
Discussion
hmmm, Have you tried installing ReadEra?
I didn't understand, If she using an Android Tablet? If so ReadEra does a very good job
She doesn’t have a tablet, reading from web or Apple App Store app. But wants a tablet and I noticed both of the places she reads from have an android app. Otherwise she had to read from web which I think is not as nice as the apps - or so she tells me.