Read the Docs tutorial
https://docs.readthedocs.io/en/stable/tutorial/index.html

forked
'https://github.com/readthedocs/tutorial-template' to 'https://github.com/earnhardt3rd-forks/read-the-docs-template'

Following the required setup for new ‘.readthedocs.yaml’
https://docs.readthedocs.io/en/stable/guides/setup/configuration-file.html

Added file to root of repo..

Removing the newly added '.readthedocs.yaml' allowed build to complete again..