Deleting Trello account and the board that is linked to Bitbucket will prevent further integrations

If you integrate Trello board with Bitbucket Cloud account first, then delete that Trello account without disabling the integration first and try to link that Repo Board to a new Trello board, the integration is not going to let you do that
The error you will get is "Something went wrong"
API error:

{"message": "child "user_uuid" fails because ["user_uuid" is not allowed to be empty]", "validation":\\ {"keys": ["user_uuid"], "source": "query"}

, "error": "Bad Request", "statusCode": 400}