The optional Windows 10 KB4598291 update is available for devices running the 20H2 and 2004 versions of Windows 10.
This update comes with many bug fixes.
KB4598291 is an optional update (also known as a cumulative "preview" update) which means it will not apply to your system unless you click "Download and Install" in the Settings application.
Unlike Patch Tuesday updates, this optional update comes with fixes for long-standing critical bugs.
To see the optional cumulative updates follow the path Settings - Update and Security - Windows Update - View optional updates.
2021-01 Cumulative Update Preview for Windows 10 Version 20H2 for x64-based Systems (KB4598291)
You can also download the update from the Microsoft Update Catalog, which is a free tool that can help you update your computers.
Windows 10 KB4598291 Direct Links: 64-bit and 32-bit (x86).