macOS Big Sur 11.2.1 is a maintenance update to macOS Big Sur, which was initially released in June 2020. This update addresses several issues, including:
Advanced users can use Greg Janek’s open-source script (from GitHub) to fetch any signed version directly from Apple’s content delivery network.
You will need a USB flash drive with at least of space. Plug in the USB drive and open Disk Utility . Select your USB drive and click Erase .