One could move the "statically build packages, for darwin/linux, with clang" to the "About" section on GitHub.
There are a lot of different environments which a package manager could cover. This is the most important thing for me when learning about new tools: Does it apply to my use case?
There aren't any binary packages or cache yet, but the creator of IX, Anton, has provided a rootfs tarball which uncompresses to about the same size as an installation of Ubuntu on WSL.
Also, I haven't seen anyone other than Anton add new package recipes to the IX repository. The documentation for creating package recipes is at https://stal-ix.github.io/PKG , but it's not referenced by any other page on the stal/IX website.