The software behind Codeberg is Forgejo, which is a fork of Gitea. The team of Forgejo is working on a federation protocol based on ActivityPub. Once it is done, it will be able to exchange data with other Forgejo servers and any server supporting that protocol. So, we may expect that Codeberg will transform from centralized to federated.

sr.ht chooses another approach. You only need an email to submit codes, file issue, join discussion, etc. From perspective of source hosting, it is centralized. But, from perspective of project collaboration, it is decentralized.