Microsoft released the monthly "C" release preview cumulative update with non-security improvements and fixes for Windows 10 Versions 2004 and 20H2. Both versions are receiving the same KB5000850 (https://support.microsoft.com/en-us/topic/march-25-2021-kb5000850-os-build-18363-1474-preview-ffd0a98f-4114-4883-ab1f-8d0971f63978) with a long list of key changes which can be viewed in the KB article. Note, however, if you installed earlier updates, only the new fixes contained in this package will be downloaded and installed on your device.
Prerequisite:
Microsoft now combines the latest servicing stack update (SSU) for your operating system with the latest cumulative update (LCU). If you encounter the error, 0x800f0823 – CBS_E_NEW_SERVICING_STACK_REQUIRED, close the error message and install the last standalone SSU (KB4598481 (https://support.microsoft.com/en-us/topic/servicing-stack-update-for-windows-10-version-2004-and-20h2-january-12-2021-c8a86bf7-6d49-b7fe-4369-44b1429b33cf)) before installing this LCU. You will not need to install this SSU (KB4598481) again for future updates.
To download and install the update, go to Settings -> Update and Security -> Windows Update and select Check for updates. To get the standalone package for this update, go to the Microsoft Update Catalog (https://www.catalog.update.microsoft.com/Search.aspx?q=KB4601382) website.
Note: This update also removes the Microsoft Edge Legacy desktop application that is out of support and installs the new Microsoft Edge. For more information, see New Microsoft Edge to replace Microsoft Edge Legacy with April's Windows 10 Update Tuesday release (https://aka.ms/EdgeLegacyEOS).
Windows 10 update history (https://support.microsoft.com/en-us/topic/windows-10-update-history-53c270dc-954f-41f7-7ced-488578904dfe)