Today, Microsoft announced that the official SDK for the Windows 10 May 2020 Update is now available with a go-live license. That means that apps targeting Windows 10 version 2004 can now be published on the Microsoft Store.
There are a few key new features and APIs that Microsoft highlighted in its blog post. One is the Windows Subsystem for Linux 2. Shipping in version 2004, WSL 2 actually includes the Linux kernel. There's a new Hosted App Model, which lets apps set themselves as hosts for other apps. The third feature highlighted is Sparse Signed Packages, which you can learn more about here.
Right now, you can get the new SDK by going through the Visual Studio Installer, and then choosing -> Individual Components -> SDKs, libraries, and frameworks -> Windows 10 SDK (10.0.19041). Once the Windows 10 May 2020 Update is generally available though, it will be included by default in the UWP development package.
We're still expecting that to be a couple of weeks away though. Microsoft was originally planning to ship the May 2020 Update earlier in the month, but it had to patch a zero-day security flaw first.