tangled.org writes issues as atproto data that lives in a user's PDS which is one neat idea.

Radicle stores issue & PR data as git objects. This approach interests me because issue data is as important as the code so we should treat it with the same care as the code. I.e. a tamper-proof cryptographic chain, signed objects, distributed redundancy, well-tread management features like synchronization and packfiles, etc.