Hmm, your nginx.conf looks about right. You even got the resolver for the docker network internal dns server covered.
I don’t remember ever using proxy_redirect off; and I am not sure if the missing space in upstream frontend_server{ has any negativ affect. Appart from that everything looks fine.
This is how I used to make the reverse proxy rule:
Use to make, because I switched to Traefik and it’s container/service label based rules…