If you only need a bare minimum, and don’t plan to heavily use CI/CD, container/packages registries, integrations with other tools i would go with gitea/forgejo (you can always use external tools on top), else i would use selfhosted Gitlab, it has pretty much all the things you could imagine to need with software development and deployment
Suzy-Q cable is used to low-level interact with newer chromebooks firmware, you can for example disable firmware write protection (previously it was done with a screw), debug hardware and unbrick chromebook
you can read on it a bit more in official Google docs: https://chromium.googlesource.com/chromiumos/third_party/hdctools/+/HEAD/docs/ccd.md