IMHO, if the protocol specifications seem like pedantry to you the best thing to do is either drop it or design your own protocol. But if in the end what you do is to release a product that is only half-compliant, the rest of the community will turn their backs on you because, by not complying with the standard, you can produce all kinds of unexpected situations.

Restic (or rustic) and Hetzner storage box 🤩

Or you can directly use Glowing Bear without installing anything.

Well, if you want private images it is normal that they charge you for it. What I advise you to do is to make the images public and mount the private part as a volume. This way you can upload the images wherever you want without worrying.

Another option if you want the resulting image to have something private is to create as much as you can in a public image and have a script that adds the private part as the last layer.

Apart from the registries you have in GitLab and GitHub if you are looking for something more generic like Docker Hub you have Quay (from RedHat). It works very well and has a pretty nice interface (especially the new one that is in testing).

You don’t really need Cloudflare to have your own domain, you can do everything directly with GitHub.