The MP uses a template, in which the initial discovery is targeted at the Microsoft.SystemCenter.RootManagementServer class. This class has been obsolete since SCOM 2012.
However, this choice of target makes it impossible to control where the monitoring workflows run. That can be remedied by adding a Resource Pool and using that as the discovery target. Directing the workflows is then done simply by populating that resource pool with specific Management Servers. The code for his is not very complicated; I'd be happy to help if needed.