Microsoft have finally released a 19H1 build of Windows 10 to the slow ring. Due to an issue with anti-cheat software causing Windows to crash Microsoft have held back 19H1 builds from the slow ring, but Microsoft have added a check so that if you have a game effected by this issue you won’t receive the build. Microsoft don’t actually say which games are causing the issue.
18342 has Linux Subsystem for Windows and the Windows file system integration.
Here is my hands on video with 18342: