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

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

⚠️Nginx proxies configured without a resolver will cache IP addresses and cause your site to go offline without warning whenever our underlying infrastructure changes. You must use a resolver configuration when proxying with nginx.

The below configuration has been tested and works with these exact settings if there are no conflicting top-level config issues.
server {
    listen 80;

    server_name <>; # Replace with your domain

    # include any global or shared config
    # include /etc/nginx/conf/your-config-here.conf;
    # redirect to SSL
    return 301 https://$host$request_uri; 

server {
    listen 443 ssl default_server;

    server_name <>; # Replace with your domain

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

    location /blog/ {
        client_max_body_size 10G; # Required for uploading large files
        # Proxy Settings, all required
        resolver; # Prevent caching the upstream IP - use preferred DNS resolvers or leave as default
        set $ghost_url https://<yoursubdomain>; # Replace with your subdomain
        proxy_pass $ghost_url; # Variable name must match line above, use of variable required for resolver
        proxy_redirect off;
        proxy_set_header Host <yoursubdomain>; # Replace with your subdomain
        proxy_set_header X-Forwarded-Host <>; # Replace with your domain
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;