Pocketbook also makes great devices, not that well known outside of EU but their software has more features than Kobo and is (as of yet) not in the book selling market so no conflict of interest (and no analytics, contrary to kobo).

Export your OTP database to an (optionally) encrypted file on a USB stick and put that in a lockbox/somewhere safe. If encrypting the stick/file: make sure you use a memorized/written down password.

After updating my uBlock lists to the latest version the popup no longer appears. Something to try out.