we got a similar configuration on may sites, only haproxy instead of nginx, but the flow is the same and I’m not encountering your issue. This gives me a first question for you: Did you setup a domain for the website setting port and protocol too? Did not try it yet but it could force base url creation with http protocol and thus the issuee you’re encountering.
maybe I misunderstood something, but I would not like to mislead you.
I was referring to the Neos backend Site Management configuration area, where you can set a domain, port and host for a website.