@Nubi-KR and @dunlix thank you separately for your interest and assistance.

@pitaj you are perfect.!
worked and the nodebb forum is online. I am very happy.
thank you so much.

@dunlix I do not know how to do it. I haven't configured the machine for this, I just access it with nodebb, mongo, nginx installed and putty.
I am using aws ec2 ubuntu.

[Edit]
is there any way to do this with putty?

@pitaj
gave an output as follows

@pitaj yes i tried the same steps again. unfortunately no improvement

my website;
13.59.185.135:4567
gundemly.com

https://imgur.com/a/IdZhjJ6

@nubi-kr said in After installing on Ubuntu, only seeing the "welcome to nginx" page:

@selmank
need more information to know what is problem

1. check ipaddress:4567
2. check domain.com:4567

I think something is wrong with 'Configuring nginx' part

@nubi-kr
Thanks for the reply. We changed only 'server_name' in this file, other configs same.

server {
    listen 80;

    server_name forum.example.com;
    
    access_log /var/log/nginx/forum.example.com.access.log;
    error_log /var/log/nginx/forum.example.com.error.log;

    location / {
        proxy_set_header X-Real-IP $remote_addr;
        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header Host $http_host;
        proxy_set_header X-NginX-Proxy true;

        proxy_pass http://127.0.0.1:4567;
        proxy_redirect off;

        # Socket.IO Support
        proxy_http_version 1.1;
        proxy_set_header Upgrade $http_upgrade;
        proxy_set_header Connection "upgrade";
    }
}

I followed the instructions here;

How to install NodeBB Forum with Nginx and Let's Encrypt SSL on Ubuntu 20.04 LTS

NodeBB is a modern forum software powered by Node.js which uses MongoDB/Redis as database platforms. It uses web sockets for instant interactions and ...

HowtoForge (www.howtoforge.com)

We followed the steps in the "https://docs.nodebb.org/installing/os/ubuntu/" link, but only the Nginx login page appears when accessing the address.

We use Nodebb 16.x, node.js 12.x