Windows 10 Versions 1903 and 1909 support WLS2

Microsoft issued an announcement stating that in view of the needs of users to expand the accessibility of WSL 2, after months of exploration, the company has backported WSL 2 to Windows 10 versions 1903 and 1909.
According to Microsoft, at present, the reverse porting for versions 1903 and 1909 is only applicable to x64 systems. If the user is using the ARM64 version, they need to upgrade to Windows 10 version 2004 to get full access to WSL 2. To get this backport, users only need to check for updates on Windows Update.
Microsoft writes:

You can check if you have this backport by verifying the minor build number of your Windows build. To do this, right click on the start menu, click ‘Run’ and then type in ‘winver’ and hit enter. The first number before the . is your major build number, so for version 1903 this will read 18362. The number after the . is your minor build number, and this will let you know whether you have the backport on your machine. This backport has the minor build number: 1049. To summarize, if your minor build number is 1049 or higher on Windows builds 18362 or 18363, then you have the backport and the ability to run WSL 2 distros.

Detailed installation/update instructions can be found in the official documentation.