Not working at all (probably a configuration issue)

[wodim]

What could be wrong here? nginx 1.15.9

server {
        listen 80;
        listen 443 ssl http2;
        server_name xxx;
        charset utf-8;
        default_type text/plain;

        ssl_certificate /etc/letsencrypt/live/xxx/fullchain.pem; # managed by Certbot
        ssl_certificate_key /etc/letsencrypt/live/xxx/privkey.pem; # managed by Certbot

        if ($scheme = http) {
                return 301 https://$server_name$request_uri;
        }

        autoindex on;
        root /var/www/xxx/;

        location / {
                fancyindex on;              # Enable fancy indexes.
                fancyindex_exact_size off;  # Output human-readable file sizes.
        }

        location /unlisted {
                autoindex off;
        }
}

[SubrataM3]

You should try turning off autoindex at server block.
OR

location / {
   autoindex off;
   fancyindex on;              # Enable fancy indexes.
   fancyindex_exact_size off;  # Output human-readable file sizes.
 }

I think they are conflicting.

[wodim]

True, thank you.