According to this thread, repo admins can install GitHub Apps on the repos they have admin permissions.
I created a small GitHub App to test this, but I can only see organizations for which I’m an owner. I’m not owner of the missing organization, but I am admin on a number of repos belonging to that organization.
Are there additional restrictions for installing GitHub Apps for repo admins? Is there a specific organization setting that needs to be enabled to allow repo admins to install GitHub Apps?
The documentation on GitHub Apps seems to be outdated on this (if the information on the thread above is correct, see https://developer.github.com/apps/differences-between-apps/#what-can-github-apps-and-oauth-apps-access):
Only an organization owner can install a GitHub App on their organization