Windows 10, version 1903 (also known as the Windows 10 May 2019 Update) is reaching end of service on December 8, 2020. Microsoft advises customers to upgrade as soon as possible to the latest on-premise or cloud versions to keep systems bug-free and secure from attacks. Microsoft previously delayed the end of support for several editions of Windows 10 version 1803 and version 1809 to May 11, 2021, due to the current public health situation. Microsoft to automatically update devices to version 2004 by manually seeking for updates via Windows Update.
Source: https://www.bleepingcomputer.com/news/microsoft/microsoft-windows-10-1903-support-ending-in-december-2020/