In the last weeks Microsoft has released the 2 1st builds of 20H1 for users on the skip ahead update ring. These builds are from the 20H1 development branch. 20H1? not 19H2? here’s why:

“Some things we are working on in 20H1 require a longer lead time. We will begin releasing 19H2 bits to Insiders later this spring after we get 19H1 nearly finished and ready; once 19H1 is “nearly finished and ready” we’ll also use the Release Preview ring for previews of drivers and quality updates on 19H1.”

Running smooth for now, only thing I ran into up to now is a 2 sec black screen when switching to battery saver. Enjoy upgrading & testing!

IMPORTANT: As is normal with builds early in the development cycle, builds may contain bugs that might be painful for some. If you take this flight, you won’t be able to switch back to the Fast or Slow rings without doing a clean-install on your PC and starting over.

If you are looking for a complete look at what build is in which Insider ring – head on over to Flight Hub. You can also check out the rest of our documentation here including a complete list of new features and updates that have gone out as part of Insider flights for the current development cycle.

General changes, improvements, and fixes for PC

• REMINDER: The new tamper protection setting in the Windows Security app protects your device by helping to prevent bad actors from tampering with the most important security settings. The setting is designed to be on by default, however the default state is not currently in effect for current Insider Preview builds. You may see a new recommendation in the Windows Security app suggesting you turn this setting on.
• We fixed an issue where turning off Location from the Action Center might take multiple clicks to react.
• We fixed an issue resulting in being unable to re-arrange pinned folders in Start’s tile grid.
• We fixed an issue where newly installed apps might not show up in search results.
• We fixed an issue resulting in some Insiders not being able to open Cortana when in Tablet Mode.
• We fixed an issue from the previous flight where right-clicking the desktop would bring up a light colored context menu in dark theme.
• We’re updating the name of the “Windows Light” theme to now be “Windows (light)”.
• We fixed an issue where Cortana’s icon on secondary monitors wouldn’t update colors after switching between light and dark theme.
• We fixed an issue where when using light theme + small icons + a vertical taskbar orientation, text written on the taskbar would stay white and thus wouldn’t be readable.
• We fixed an issue that could result in open apps not being shown on the taskbar (but being visible in Alt + Tab).
• We fixed an issue resulting in build unable to log into WinRE with an admin account in the last couple of flights.
• We’ve made another fix to address reports of devices getting stuck with “Hibernating…” text on the screen on resume from hibernate.
• We fixed an issue resulting in greys having an unexpected slight pinkish/purple-ish tinge on some devices in recent flights.
• We fixed an issue in Ease of Access’s Cursor and pointer settings, mouse pointer size and color are now retained on upgrade.
• We fixed an issue where the Windows Security app may show an unknown status for the Virus & threat protection area, or not refresh properly.
• The issue impacting Creative X-Fi sound cards has been fixed. It’s not fixed.
• [ADDED 2/15] We added the ability for users to access Linux files in a WSL distro from Windows. These files can be accessed through the command line, and also Windows apps, like File Explorer, VSCode, etc. can interact with these files. Access your files by navigating to \\wsl$\<distro_name>, or see a list of running distributions by navigating to \\wsl$.
• [ADDED 2/15] We improved the capabilities of the wsl.exe command line interface, by adding new features such as importing and exporting distros and consolidating existing features from wslconfig.exe, such as listing distros and setting defaults.

Known issues

• Launching games that use anti-cheat software may trigger a bugcheck (GSOD).
• While we’ve done some work to improve night light reliability in this build, we’re continuing to investigate issues in this space.
• When performing Reset this PC and selecting Keep my files on a device that has Reserved Storage enabled the user will need to initiate an extra reboot to ensure Reserved Storage is working again properly.
• Some Realtek SD card readers are not functioning properly. We are investigating the issue.
• File Explorer may hang when trying to rename, delete, or move MKV files.
• In Windows Sandbox, if you try to navigate to the Narrator settings, Settings app crashes.
• Creative X-Fi sound cards are not functioning properly. We are partnering with Creative to resolve this issue.

source: Windows Blogs