As a user, how can I determine the installed version of GitHub Enterprise?

As a GHE admin, I don't think that the version is displayed to non-admin users, even in the API meta information or page source, etc.

However, for admins, it is displayed in a bar across the top of every page. So, if you do ask them, they'll have that info readily available on their screen if they're logged in.

I was searching for the same information for our github enterprise version. In the page source I found the following:

<a href="/">
      <span class="octicon-mark-github" title="GitHub Enterprise Version 11.10.xxx"></span>
</a>

This is the GitHub Octocat logo in the footer of GitHub Enterprise - just hover over it to get a tooltip with the version number.

I realize this isn't extremely user friendly, but it is available to any user even if not logged in.

Since Github Enterprise v2.12, you can get the GitHub Enterprise version from the service's /meta API endpoint. The returned JSON will include an installed_version field containing the version number.

https://ghe.company.com/api/v3/meta

{
  "verifiable_password_authentication": true,
  "installed_version": "2.20.0"
}

If connecting to api.github.com, the JSON returned from GitHub's /meta API endpoint will have other additional fields but will not include an installed_version field.

https://api.github.com/meta

{
  "verifiable_password_authentication": true,
  "ssh_key_fingerprints": { ... },
  "hooks": [ ... ],
  "web": [ ... ],
  "api": [ ... ],
  "git": [ ... ],
  "pages": [ ... ],
  "importer": [ ... ]
}

I found that if you go to the GHE Home page and scroll to the bottom, you can find the version mentioned as shown in the snapshot