git was designed to be decentralized. Everyone can (technically, but it is not too hard to set up if you have some affinity with servers) fork/clone another git repository and serve it up. It has built-in ways to synchronize with any other server. In fact, that synchronizing is what most developers do when they use git.

Of course, that would make it harder to know which repository has the "official" version, but in a way, that is maybe also a benefit of decentralisation. Knowing what code is authentic can be done by signing the commits.

The hubs that we see, are usually a combination of git and a way to serve the code, along with documentation, roadmap, bug tracking, automatic testing and building and the resulting binaries in a visually pleasing way. That does not need to be a part of decentralizing the code, and it is not the only way to do it.

Some of that can also be done with git built-in tracking of files, and the building and testing can probably also done in other locations, as long as there are files describing how to do that bundled with the code (which practically all projects already do).

Sourcehut (https://sr.ht) is one hub that helps developers use simpler tools for those workflows, and I think that's a good place to find some inspiration.