Some projects purpose built to enable actions automation at scale:

GitHub Docs: About enabling advanced setup for code scanning with CodeQL at scale

Script based solutions:

• https://github.com/NickLiffen/ghas-enablement
• https://github.com/Malwarebytes/ghas-cli

GH Cli:

• https://github.com/advanced-security/gh-add-files

Generic:

• https://github.com/jhutchings1/Create-ActionsPRs