Not exactly what you are after, but related. There is ForgeFed [0] as a standard for code forge federation. It is an extension of ActivityPub [1] social web protocol, and thus far includes all the basic elements to facilitate task management / kanban. The project is wholly volunteer-driven, and recently received NLnet support to mature the standard further. Recently the maintainers were asking for feedback to help improve the specs. Various forges such as Gitlab [2] and Forgejo [3] are adding support for ActivityPub and considering ForgeFed support too.
[0] https://forgefed.org/spec/
[1] https://www.w3.org/TR/activitypub/
[2] https://gitlab.com/groups/gitlab-org/-/epics/11247
[3] https://codeberg.org/forgejo-contrib/federation