https://wccftech.com/optional-windows-10-update-kb4601380-1909-and-1809-rolling-out/

Image: Drew Angerer / AFP / GETTY Images

Microsoft has released preview updates for Windows 10 versions 1909 and 1809. These aren't mandatory security updates and are tagged as optional, non-security, "C" updates that are tested before being part of next month's cumulative update rollout. You shouldn't install them on your primary devices, but if you are interested, you can get them via Windows Update or Microsoft Update Catalog.