Hello @JackZhang2
When you create the counter in Monitor, a service is created on the server. This service by default is created without being assigned to a user, so you will have to manually go to the service, find the domain user, assign it and set the password. Another option is to use a managed service account. This way the service will run under a domain account (domain user or managed service account).
Next, on the server to be monitored, assign the account. If its an administrator (not recommended for security) you don't have to modify the configuration, but the convenient is the process you mention, include it in "Distribute COM users" and "Performance monitor users". Also, in WMI ROOT\CIMV2 add the permissions of Enable account, Enable remote and Read security.
Doc.
https://enterprise.arcgis.com/es/monitor/10.8/administration/configure-wmi-access-for-nonadministrat...
You have a local user (computername/username), it would be necessary to test and confirm if its works on remote servers. 'Cause if you don't have an AD, maybe create a user account with the same name and password on both servers to see if it is valid (not sure if it is supported). Since the normal setup (on Windows Servers) is have computers that are in domain (Active Directory) and use either AD user accounts or managed service accounts.
In the hostname, it is convenient to use the complete host name (FQDN) (server.domain.local) or the IP address (this is not mandatory). Also confirm that the DNS resolves the FQDN, and open the ports between the servers (firewall SW/HW), WMI port 135 TCP (necessary for resource monitor) and the RDP port 3389 TCP in case you want to add this counter (RDP monitor).
Regards.
