Where can I report a GitHub bug?

See:

• https://support.github.com/contact/feedback
• https://support.github.com/request
• https://github.com/isaacs/github#if-you-have-an-issue-or-feature-request-for-github
• https://github.com/dear-github/dear-github
• [email protected]
• Submitting tickets using an enterprise account

The only way I know is to fill out the form at https://support.github.com/contact as far as I know they don't have a public issue tracker.