To use the Github Actions provisioner you will need to create and install a new Github App with Self-hosted runners Read & Write permissions on the organization level and provide your config with the respective information.
While trying to create such an app I stumble upon 'Callback URL' field. It's required, but I can't fully understand what URL to provide.
I've accidentally toggled on 'Request user authorization (OAuth) during installation', that was causing Callback URL field to be required. Toggling off solved the problem.
Your guide provides following step:
While trying to create such an app I stumble upon 'Callback URL' field. It's required, but I can't fully understand what URL to provide.