Which type of node can function as a NTP server for the vRealize Operations cluster...

According to the VMware vRealize Operations Reference Materials, primary nodes are responsible for managing the cluster configuration and synchronizing data across the cluster. They can also function as NTP servers for the cluster, ensuring that all nodes have the same time settings. Remote collector nodes, replica nodes, and data nodes rely on the primary nodes for NTP settings and cannot act as NTP servers themselves. References:

vRealize Operations Manager Cluster Node Types

Configuring NTP Settings