https://docs.openshift.com/container-platform/4.9/service_mesh/v2x/ossm-federation.html#exposing-the-federation-ingress-on-clusters-running-on-bare-metal are the appropriate instructions to use when deploying Federated Service Mesh on Z & P, but this fact needs to be presented in the documentation for OSSM 2.1 on OCP 4.6, OCP 4.7, OCP 4.8 & OCP 4.9. 

Also, when federating across network boundaries there are a variety of environmental 'tweaks' that need to be done on both hosts for DNS configuration, firewall changes and load balancer changes.  While these will be different for each client's environment, we developed some scripts to test federation in a variety of Z & P environments in https://github.com/IBM/OSSM-federation-zap-config that might be useful to mention in the 'expanded bare metal' documentation above.