This should be the Registration UI
You ended up here because you didn't set the following configuration value:
path/to/kratos/config.yml
selfservice:
flows:
registration:
ui_url: http://my-app.com/registration
You can set this configuration value using environment variable SELFSERVICE_FLOWS_REGISTRATION_UI_URL
as well!
If you don't know what that means, head over to Self-Service User Registration!