There is an extra step needed for broker version 7.9.3:

iv. Deploy the security CRD:
oc create -f deploy/crds/broker_activemqartemissecurity_crd.yaml

Reported by: hdaems

https://access.redhat.com/documentation/en-us/red_hat_amq/2021.q3/html/deploying_amq_broker_on_openshift/deploying-broker-on-ocp-using-operator_broker-ocp#annotations:3fc71a5c-0a95-413d-b6af-21fd5f8cdd52