Parse HTML as PHP on a Azure App Service (Linux) running PHP 8.1

I am really struggling to get an Azure App Service running Linux and PHP 8 or 8.1 to parse HTML files through PHP. The 8.0 and 8.1 versions run on nginx rather than Apache.

I have started by updating the nginx blocked used by the app service, located at /etc/nginx/sites-enabled/default, to read the below. This is as per default, except adding the HTML location alongside PHP:

server {
    listen 8080;
    listen [::]:8080;
    root /home/site/wwwroot;
    index  index.php index.html index.htm;
    server_name  example.com www.example.com;
    port_in_redirect off;

    location / {
        index  index.php index.html index.htm hostingstart.html;
    }

    error_page   500 502 503 504  /50x.html;
    location = /50x.html {
        root   /html/;
    }

    location ~ [^/]\.(php|html)(/|$)  {
        fastcgi_split_path_info ^(.+?\.php)(|/.*)$;
        fastcgi_pass 127.0.0.1:9000;
        include fastcgi.conf;
        fastcgi_param HTTP_PROXY "";
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        fastcgi_param PATH_INFO $fastcgi_path_info;
        fastcgi_param QUERY_STRING $query_string;
        fastcgi_intercept_errors on;
        fastcgi_connect_timeout         300;
        fastcgi_send_timeout           3600;
        fastcgi_read_timeout           3600;
        fastcgi_buffer_size 128k;
        fastcgi_buffers 4 256k;
        fastcgi_busy_buffers_size 256k;
        fastcgi_temp_file_write_size 256k;
    }
}

This correctly then attempts to parse HTML files through PHP, however they all then display the following error:

NOTICE: Access to the script '/home/site/wwwroot/login.html' has been denied (see security.limit_extensions)

I have then gone to /usr/local/etc/php-fpm.d/www.conf and added the following line:

security.limit_extensions = .php .php3 .php4 .php5 .php7 .html Normally, this would then work. Under an App Service however, I still receive the security.limit_extensions error message. Running php-fpm -tt appears to show the correct settings are in place and applied.

Other posts reference SeLinux, which doesn't appear to be running, and cgi.fix_pathinfo which is set to 1.

I am aware the above files do not maintain on app services after a restart, but are currently in place.

Has anyone (Please!!) got this to work and successfully parsed HTML as PHP on PHP8.1, as an Azure App Service?