WordPress added official ActivityPub plugin so I tried it.

From my quick test, having two blogs in subdirectory of same domain doesn’t seem to work. As I don’t care about the main blog on top directory, I added specific rule for the relevant /.well-known/ endpoint:

location ^~ /.well-known/ {
  try_files /index.php =404;
  include wpmu_headers.conf;
  include php.conf;
  fastcgi_pass wpmu;
  fastcgi_param REQUEST_URI /blog$request_uri;
}

The main key is pointing to correct index file as per usual nginx and prefixing the url passed to WordPress with the correct subdirectory prefix.

And then things seem to just work 🤷‍♀️

(this post also serves as test post to see if it appears on timeline after following)