There have been many experiments with adding simple ActivityPub support to static blogs, enabling authors to publish their blog into the fediverse to be followed and get commented on. Some of these experimenters have documented what they did, and I've started a list of examples here;
https://codeberg.org/fediverse/fediparty/wiki/Fediverse-comments-on-static-blogs
I chucked this together in a hurry, so please prod me about any mistakes, or any additions that could be made to the list.