Basically, you’re running into this (as far as I understand from your post)
uri cannot rewrite responses, it only rewrites the request on the way in.
I’m not sure I understand what you’re trying to do though. Where is this file you’re trying to serve? Is it actually on disk at /var/opt/website/home/core/img/manifest.json? That’s where file_server is looking for it with your current config.
Please don’t forget to persist /data when running in Docker, especially when using Let’s Encrypt for certificates, otherwise you’re throwing away your certificates and keys every time you re-create your Caddy container. Docker
For what it’s worth, I’d write your config (what you have so far) like this:
redir /nc /nc/
handle_path /nc/* {
reverse_proxy https://XXXXXX.net:2443
}
handle {
root * /var/opt/website/home
file_server {
index index.html index.htm
}
}