If you want users to log in to your Joomla site using their GitHub credentials, you can do it using our Joomla GitHub OAuth plugin. Once you configure the GitHub with the Joomla OAuth plugin, you can allow GitHub users to SSO into your Joomla site using GitHub.
Similarly, you can map your Joomla roles based on your GitHub attributes/groups. To know more about other features we provide in Joomla OAuth plugin, you can download by click here.