Per discussion by email:

We now have a new request from upper management to enable OpenShift Container Platform for IBM Z before the end of the calendar year. As we did with Power LE, we need to provide the OpenJDK containers listed below in order to allow building Java applications through ImageStreams:

redhat-openjdk-18/openjdk18-openshift (redhat-openjdk-18-openjdk18-openshift-container)
openjdk/openjdk-11-rhel7 (openjdk-11-rhel7-container)
openjdk/openjdk-8-rhel8 (openjdk-8-rhel8-container)
openjdk/openjdk-11-rhel8 (openjdk-11-rhel8-container)

Following the agreement from middleware teams that the hawkular-javaagent jar bundled in the OpenJDK containers is unused and therefore its lack of s390x support can be ignored, there should be no further technical blockers to enabling these on Z. The remaining engineering work will be for RCM to modify the container build tags, and to add s390x content sets to the YAML files. As before, I can help with this effort.

We do understand that RHEL OpenJDK is not yet TCK-certified on Z, and this is not a requirement at this time. We also understand that there is a performance gap between 8 and 11 on Z. This is acceptable as this is simply meant to allow S2I based on RHEL content.