For adding hosts via API day2 operation, existing documentation includes instruction to boot only with ISO(Step 5,6 and 7 in https://docs.redhat.com/en/documentation/assisted_installer_for_openshift_container_platform/2026/html/installing_openshift_container_platform_with_the_assisted_installer/expanding-the-cluster#adding-hosts-with-the-api_expanding-the-cluster). 

However, on zVM and LPAR, user will have to use PXE booting as ISO booting is not supported. This info is missing in the documentation.

4.22.0-ec.2