OpenJDK 10 doesn't contain the flight recorder.
There's one area tiny though where there's a significant difference between 10 and 11- Flight Recorder is now open source. That's a fairly good reasoning and perhaps an apt-get upgrade wouldn't screw things up that badly when OpenJDK's version gets bumped up from 10 to 11. This choice was based on that assumption that there is a much smaller interface delta between releases 10 and 11 than it would be between 8 and 11. Although version 10 is a non-LTS release, they've packaged it as openjdk-11-jdk until OpenJDK 11 goes GA. The Ubuntu Foundation Team made an SRU exception for OpenJDK. After having it installed on Ubuntu 18.04 (Bionic Beaver), which comes with a package named openjdk-11-jdk, to my surprise, that was still part of an earlier version (Java 10).
As this is the first LTS release after version 8, it's been a long time coming. OpenJDK 11 was released on September 25, 2018.
