My standard flyctl test image :)

Dockerfile

FROM nginxdemos/hello:latest
RUN rm /etc/nginx/conf.d/hello.conf
ADD hello.conf /etc/nginx/conf.d/

hello.conf

server {
    listen 8080;
    listen [::]:8080;

    root /usr/share/nginx/html;
    try_files /index.html =404;

    expires -1;

    sub_filter_once off;
    sub_filter 'server_hostname' '$hostname';
    sub_filter 'server_address' '$server_addr:$server_port';
    sub_filter 'server_url' '$request_uri';
    sub_filter 'server_date' '$time_local';
    sub_filter 'request_id' '$request_id';
}