We should also think of updating the startup scripts to pass --enable-preview to JVM if exactly Java 19 is detected. Elasticsearch and Opensearch will / have already done this. Not doing this will print a startup warning on Java 19 to Java logging.
The main reason to pass --enable-preview to the JVM is to allow MMapDirectory V2 to be enabled and memory mapping happening in larger junks for less overhead and use of kernel resources (see vm.max-map-count sysctl). It also reduces risk of crushing JDK on bad written plugins or bugs with reopening IndexSearcher/IndexReader.
See https://github.com/apache/lucene/pull/912 for more details.