@spivi

For the WordPress rewrite, i.e

    location /subdir {
        try_files $uri $uri/ /subdir/index.php?$uri&$args;
    }

Try changing that to:

    location /subdir {
        try_files $uri $uri/ /subdir/index.php?$args;
    }

… and then reloading NGINX for the changes to take. I use the same on a dev Droplet as well as many live instances that I work on for various clients and that has always worked.

Sure, here you go:

server {
    listen 443 ssl http2;
    listen [::]:443 ssl http2;
    server_name www.domain.com;
    root /home/forge/www.domain.com/public;

    server_tokens off;

    # ssl info...

    add_header X-Frame-Options "SAMEORIGIN";
    add_header X-XSS-Protection "1; mode=block";
    add_header X-Content-Type-Options "nosniff";

    index index.html index.htm index.php;

    charset utf-8;

    ##############################
    ## Kirby configuration
    ##############################

    if (!-e $request_filename){
      rewrite ^/panel/(.*) /panel/index.php break;
    }

    if (!-e $request_filename){
      rewrite ^/subdir/(.*) /subdir/index.php break;
    }

    if (!-e $request_filename) {
      rewrite ^/(.*)$ /index.php last;
      break;
    }

    location /content {
      rewrite ^/content/(.*)\.(txt|md|mdown)$ /error redirect;
    }

    location /site {
      rewrite ^/site/(.*) /error redirect;
    }

    location /kirby {
      rewrite ^/kirby/(.*) /error redirect;
    }

    location ~* \.(ico|css|js|gif|jpeg|jpg|png|woff|ttf|otf|svg|woff2|eot)$ {
        expires 1M;
        add_header Pragma public;
        add_header Cache-Control "public";
    }

    ##############################
    ## End Kirby CMS configuration
    ##############################

    location / {
        try_files $uri $uri/ /index.php?$query_string;
    }

    # Wordpress subsite
    location /subdir {
        try_files $uri $uri/ /subdir/index.php?$args;
    }

    # panel links
    location /panel {
        try_files \$uri \$uri/ /panel/index.php?\$uri&\$args;
    }

    location = /favicon.ico { access_log off; log_not_found off; }
    location = /robots.txt  { access_log off; log_not_found off; }

    access_log off;
    error_log  /var/log/nginx/www.domain.com-error.log error;

    error_page 404 /index.php;

    location ~ \.php$ {
        fastcgi_split_path_info ^(.+\.php)(/.+)$;
        fastcgi_pass unix:/var/run/php/php7.1-fpm.sock;
        fastcgi_index index.php;
        include fastcgi_params;
    }

    location ~ /\.ht {
        deny all;
    }
}

I might have gotten it from here: https://gist.github.com/ramv/9402198

It looks like it’s not necessary per se, but it’s meant to return the Kirby 404 template for URLs with file extensions where the files don’t actually exist. It’s essentially an Apache -> nginx translation of the following lines in the default Kirby .htaccess file:

# make panel links work
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^panel/(.*) panel/index.php [L]

# make site links work
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{REQUEST_FILENAME} !-d
RewriteRule ^(.*) index.php [L]