Recommended nginx config for Ghost(Pro) subdirectory proxy. SSL is required.

nginx.cnf

server {
    listen 80;

    server_name <yourdomain.com>; # 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 <yourdomain.com>; # 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 1.1.1.1 8.8.8.8; # Prevent caching the upstream IP - use preferred DNS resolvers or leave as default
        set $ghost_url https://<yoursubdomain>.ghost.io; # 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>.ghost.io; # Replace with your subdomain
        proxy_set_header X-Forwarded-Host <yourdomain.com>; # Replace with your domain
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
    }
}