Can we install secondary hub in cluster?
This is not currently considered supported - we have not tested or certified running secondary hubs on a cluster, and there are potential side-effects related to hub-to-hub communication which may be of concern.
The only supported method for high-availability of a secondary hub is the use of the UIM HA probe:
https://docops.ca.com/ca-unified-infrastructure-management-probes/ga/en/alphabetical-probe-articles/ha-high-availability