refer to this ACM document - https://access.redhat.com/documentation/en-us/red_hat_advanced_cluster_management_for_kubernetes/2.5/html/multicluster_engine/install-on-disconnected-networks#installing-in-a-disconnected-environment

the mcgh registry can be registry.redhat.io/mcgh or registry.redhat.io/multicluster-globalhub. 

once we have a bundle building, we can use oc mirror command to mirror the operator, images, and generate a catalogsource for disconnected environment.