It's possible to setup a reverse proxy using Apache to establish a subdirectory on Ghost(Pro).

For this configuration to work successfully, you must be on a Business plan with a subdirectory enabled via [email protected]. You must also paste the exact configuration below into your apache configuration file, updating each line as specified so that it meets our reverse proxy rules.

The below configuration has been tested and works with these exact settings if there are no conflicting top-level config issues.
# You'll need to enable the ssl, proxy and proxy_http modules:
# sudo a2enmod ssl proxy proxy_http

<VirtualHost *:80>
    # Replace with your domain
    ServerName <yourdomain.com> 
    # Replace with your domain
    Redirect permanent / https://<yourdomain.com>  
</VirtualHost>
<VirtualHost *:443>
    # Replace with your domain
    ServerName <yourdomain.com> 
        
    SSLProxyEngine on

    # Your SSL Certificate details. Replace with your own SSL setup
    # SSLCertificateFile /path/to/cert
    # SSLCertificateKeyFile /path/to/key;

    <Location "/blog">
        # Replace with your subdomain, https matters here
        ProxyPass https://<yoursubdomain>.ghost.io/blog
    </Location>
</VirtualHost>