To update Ironkey D300SM (Serialized Managed) encrypted USB drive for macOS Big Sur, click on the link below to download the IKD300SM_v6_4_Updater.exe and IKD300SM Updater Instructions.
Note: Please read the updater instructions in its entirety prior to running the update.

Updater: https://media.kingston.com/support/downloads/IKD300SM_v6_4_Updater.zip

macOS: Must update on Windows based system. IKD300SM_v6_4_Updater.exe not supported on macOS.