Older Kindles (very old - like 4th gen) will have expired root certificates, so you'll need an unencrypted version if you want the site to be accessible by thos

Older Kindles (very old - like 4th gen) will have expired root certificates, so you'll need an unencrypted version if you want the site to be accessible by those users. I'm not aware of any comprehensive documentation on this subject though. I'd say that if the site works on your 7th gen paperwhite it will probably work for the majority of users, although there are definitely a few old units still out there from the ~2011 heyday.