Monitor the services for Azure AD Connect (Azure AD Sync). This is based on the services and performance counters that are present on the system as of Azure AD Connect 126.96.36.199 and Azure AD Connect Health 188.8.131.52., running on Windows Server 2019 build 1809.
NOTE: Not all environments will have the full set of the Azure AD Connect Health Sync Monitoring Services running, as some levels require Azure AD Premium and/or extra configuration per your environment. These components can be disabled in your template configuration if necessary.
Please let me know if there are different counters or endpoints (maybe an Azure service page or API endpoint?) that you think should be included!