This was attempted multiple times in the past. None succeeded, in large parts because at a fundamental level issues are a synchronisation point, making issues part of the repository adds overhead and complexity but doesn't really give you anything, and furthermore it increases complexity for reporters.

Pagure does something like that: https://pagure.io/pagure

All the issues, wiki, PR review are stored in Git as well. You still need a Pagure instance (that you can self host if you want) to provide the web ui, but you can easily just clone the repo and put it to a different instance, keeping all your metadata.

I’ve used git-bug[1] successfully in the past for something similar but more ergonomic.

1: https://github.com/MichaelMure/git-bug

I know of an attempt to implement an approach to track issues and code in a decentralized manner with SIT[0]. Unfortunatlely the project seems to be dead.

[0] https://github.com/sit-fyi