Maybe I did not interprete it correct:
Management board is that idrac on Poweredge? There I have da RO user which I entered in “Redfish Compatible Management Controller - Username”. The password of this user in the “Password” field.
The checkmk Host (label) is named with HEC-U3-… , it is the physical location of the Poweredge. The hostname is not used, it is configured with the idrac ip adress 10.77.90.203 in the host setup.