WordPress.org
Since the plugin is available to download from WordPress.org, you can use the WordPress.org support forum to get help with the plugin or report issues. But, I do not visit the WordPress.org every day, so any questions or issues posted there might wait few days before they are answered.
Dev4Press.com
Main support forum for DebugPress is the support website on Dev4Press.com website. Dev4Press knowledge base also contains plugin documentation, filters, actions and functions references and more. Any new topic submitted through Dev4Press support forum will be answered as soon as possible, and this is the fastest way to get support for DebugPress.
GitHub.com
And, since the development is done on GitHub, you can use GitHub issues to submit questions, bugs and feature requests.