In the latest Windows 10 Insider build, Microsoft has started to test the distribution of Windows Subsystem for Linux version 2 kernels via Windows Update. Unlike WSL1, WSL2 includes a genuine open-source kernel compiled from the stable 4.19 version of Linux at Kernel.org. Microsoft has removed the Linux kernel from the Windows image and will start distributing it through Microsoft Update. BleepingComputer has not been able to trigger a kernel update via Microsoft Update, but a user posted to Reddit that they received one, as shown below.
Source: https://www.bleepingcomputer.com/news/microsoft/windows-10-tests-wsl2-linux-kernel-updates-via-windows-update/