I have tried to install Graylog in my lab.
The issue is that I cannot have HTTP access to Graylog (default port 9000).
Here you have some details :
I am running Ubuntu 20.04:
ubuntu@ubuntu:~$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 20.04.5 LTS
Graylog is running :
ubuntu@ubuntu:/home$ ps aux | grep graylog
ubuntu 1170412 0.0 0.0 6432 656 pts/0 S+ 19:28 0:00 grep --color=auto graylog
FYI I followed the steps mentioned in page Ubuntu installation
The Ubuntu host has Internet access (it is a private IP address). The IP add es 192.168.1.2 if needed (it is not reachable from Internet).
If you can check I attach here the Configuration File located at /etc/graylog/server/server.conf
I have add password_secret and root_password_sha2 to this configuration file as is indicated in the above page.
Sorry for this long email.