The primary objective of an employee self-service functionality is to give employees access to their personnel data as well as enabling them to act on certain related tasks.
I would suggest displaying the reporting Manager Name (of the primary position) on the ESS workspace just like the position description is visible. This will help the employee to know whom they are reporting to, considering the legal entity access control which won't allow viewing the employee profile from different legal entities but allowing to view the name of the reporting manager (name as grey coloured not a hyperlink).

If the employee has permission to view data of other legal entities then viewing the reporting manager profile should be enabled (blue coloured hyperlink). Clicking on the hyperlink will open up the reporting manager's profile.