Registries are under evolution insofar as a standard was needed and changes were required for SPM to adopt that standard, which then required public changes to the package format. It seems clear Apple has no desire to build a registry themselves, instead hoping the community would build them instead. Obviously that hasn't happened, aside from support in newer versions of Artifactory (IIRC) for some reason. Whether that's due to community interest or the fact that Xcode still doesn't support registries at all I don't know. Since you're on Linux you could use them directly through SPM if there as a registry anywhere.