I can see a usecase for where you don't know where to start or search with, and then verify with actual searches.
I recently used it to explain for a friend what is the difference between wheat and ale beer, and it gave a very good summary. With DDG I might not get a direct explanation and would need to read a few articles and then word them in a comprehensive way.
As @slashzero@hakbox.social said, if you're using an additional nginx server, your docker nginx can't listen for port 80 or 443. Here's my host nginx reverse proxy's ssl section for reference:
Maybe you're missing some proxy headers, or the docker compose isn't forwarding the correct ports.
But it can definitely be something completely different.