OpenJ9 images will be deprecated. OpenJDK11 images will support IBM Z and Power architectures. The following Vert.x reference document describes the changes required P&Z. These changes are applicable for Spring Boot documentation as well.
https://docs.google.com/document/d/1eEyIqKkPA_PKjmlAVRNs8O3sg7xDFAn6HMa4enJ5Twc/edit?usp=sharing