Samsung devices are the first to receive the new September 2021 Android security patch, with all S20 models now in line for the upgrade.
The update is the firmware version G781BXXU4CUH5 and requires 790MB of space to download it. Note that it doesn’t give any new features to your S20, with the change log claiming to improve the stability of the device.
The update is being rolled out by territory, so you can check for the update by navigating to your S20/S20+/S20 Ultra’s Settings > Software update menu.