User has a repo on GitHub or Codeberg, which need to be mirrored on their bitbucket Data Center as read only. And the bitbucket must pull the current state of the repo in an configured interval.

For example, this feature is present in Gitea or GitLab. This feature is know as Pull mirror:
https://docs.gitea.com/usage/repo-mirror#pulling-from-a-remote-repository
https://docs.gitlab.com/user/project/repository/mirror/pull/

User would to get similar feature in Bitbucket Data Center.