NodeBB by default runs on port 4567, meaning that by default you must access it using a port number in addition to the hostname (e.g. http://example.org:4567)
In order to allow NodeBB to be served without a port, Nginx can be set up to proxy all requests to a particular hostname (or subdomain) to an upstream NodeBB server running on any port.
sudo apt-get install -y nginx
Verify the installation of Nginx
nginx -v
Run Nginx
sudo systemctl start nginx
sudo systemctl status nginx
Configuring Nginx
NGINX-served sites are contained in a server block which are normally stored in separate files from the main Nginx config (which is very rarely edited).
When installing with the ppa above, the best way to install new Nginx configs is to add new files in /etc/nginx/sites-available (like /etc/nginx/sites-available/forum.example.org). You then must link these files from sites-available to sites-enabled.
The following demonstrates a typical series of commands when creating a new nginx config:
cd /etc/nginx/sites-available
sudo vim forum.example.com # config entered into file and saved