Codeberg and other alternatives are used by 2 people, if not more. If a repo is hosted on such unpopular service, potential contributors must register a new account. This is very frustrating if you want to report just one issue or make one pull request. Self-hosted repos are even worse.

This problem can be solved by implementing federation. GitLab, Gitea and Forgejo already working on it, but really slow.

As far as I know, some clients have ability to add instances and you can view its local feeds without logging in

This may be more intuitive for newcomers. Matrix has something similar (matrix.to). It tells you that you want to open a chat and provides a list of apps. You can get inspiration from here.

Example: https://matrix.to/#/!matrix:matrix.org