You’re right, this looks like a bug/oversight in our documentation system. Can you find out what distribution of Linux is running on your web host, for instance by following the instructions at https://www.cyberciti.biz/faq/find-linux-distribution-name-version-number/? That may allow you to choose one of the more specific distribution drop downs.
We should update the instructions to make this situation clearer. Specifically, to summarize, if you choose “Apache” and “Web Hosting Service”, you get the instructions at https://certbot.eff.org/#sharedhost-apache, which say “… please select your server software and the operating system it is running from the dropdown menu above.” Perhaps instead we should give instructions to find out what operating system you are using, or provide “generic” instructions likely to work on most Unix-likes. @bmw @erica.