The docs for 4.20 still say

You can use any container registry that supports Docker v2-2, such as Red Hat Quay, the mirror registry for Red Hat OpenShift, Artifactory, Sonatype Nexus Repository, or Harbor.

One example here https://docs.redhat.com/en/documentation/openshift_container_platform/4.20/html-single/disconnected_environments/index#about-disconnected-environments

We should make sure to add an admonition that Docker v2-2 is deprecated in 4.20 and a future release will require OCI. That future release will be 4.21, so we should make sure that 4.21 docs only mention OCI too.