i think any reader can does this. kindle and tolino for sure. you will want to use the foss software calibre to manage your books, it can send books to kindles and will convert them when they are not in the right format. kindles cannot open epub so you have to convert to mobi or azw3 format which calibre does. ive got the current kindle paperwhite and love it. i dont read pdf on it though because its mostly a pain. i got an android tablet for pdf.
Not an extension but pihole for the wifi network and blockada on the go (android) filter a lot of tracking requests.