https://stackoverflow.com/questions/70617574/install-gitlab-community-edition-on-ubuntu-20-04

https://www.digitalocean.com/community/tutorials/how-to-install-and-configure-gitlab-on-ubuntu-18-04

Thank you for installing GitLab!
GitLab was unable to detect a valid hostname for your instance.
Please configure a URL for your GitLab instance by setting external_url
configuration in /etc/gitlab/gitlab.rb file.
Then, you can start your GitLab instance by running the following command:
sudo gitlab-ctl reconfigure