ActivityPub plugin is a very cool piece of WordPress addition. With this plugin installed users of Mastodon and other such federated platforms that support ActivityPub can follow your blog as if it were another instance on the Fediverse.

Unfortunately if you run a Bitnami instance of WordPress (for example one provided by AWS LightSail with LetsEncrypt service providing a TLS certificate for you site – you may encounter an incompatibility issue. LetsEncrypt uses /.well-known/acme-challenge path on your site for certificate validation, but ActivityPub plugin uses /.well-known/webfinger path to return relevant profile information. It conflicts with LetsEncrypt and the WebFinger path returns “404 – not found”.

Fortunately there is an easy fix.

SSH to your server, locate file /opt/bitnami/apps/letsencrypt/conf/httpd-app.conf, and add highlighted lines to it:

<Directory "/opt/bitnami/apps/letsencrypt/.well-known">
    Options +MultiViews
    AllowOverride None
    <IfVersion < 2.3 >
        Order allow,deny
        Allow from all
    </IfVersion>
    <IfVersion >= 2.3>
        Require all granted
    </IfVersion>
     
    RewriteEngine On
    RewriteBase /.well-known/
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule ^(.*)$ /index.php?well_known_path=$1 [QSA,L]

</Directory>

After that Webfinger starts returning correct profile information, and your site can be found on the Fediverse.