Currently, there isn't any Power Automate trigger to notify the Project Manager if a task item has been changed or updated.

Also, there is no role based validation to prevent someone from the team member to update or close or delete a task without the knowledge of the Project Manager. Hence, it's very difficult to adapt MS Planner Premium in any midium to large project.

It would be better if Power Autmate can be triggered if a task record is updated or deleted that would give a peace of mind for Project Manager. Alternativlly if a role-based permission control is established with in the MS Planner Premium that would help a lot.