Are you sure you on right forum? This is for forum app named Discourse, not a forum for Nginx.
But if your issue is setting up a virtual host for a forum, and using Nginx as a reverse proxy, you have to create your conf right. As changing what port a backend, here Discourse, is listening — it can’t be 80 because it is for Nginx. And then must all other needed things set up too, of course.
Or are you meaning Nginx inside Docker doesn’t work right when installing Nginx?
So, follow up depends what is your issue actually.
Sorry If I made the mistake for placing it, but I dodn’t know where to make it known
Working for many years with Ubuntu and Nginx I found the mentioned problem and yes the config files are fine and did work on a earlier version 1.22, same for php8.3-fpm that did work before and now with the newer version also doesn’t work anymore.
Docker I don’t use.
I did send a email to someone at Nginx.com but no reply received