There are several JDK options available when installing FlexDeploy. The main requirement is that the version of Java used is version 21 or 17. if your Linux distribution includes a build of OpenJDK 21 or 17, you can use that version.
Amazon Corretto - Amazon's build of OpenJDK with security updates
OpenJDK - https://adoptium.net/
Oracle JDK - Oracle's build for those who meet their license restrictions - https://www.oracle.com/java/technologies/downloads/#java21