It's official: The USBKill is a Samsung Flagship Killer.
We use the USBKill V4 Pro's "Offline Attack" mode - which requires no host post to deliver a USB Power Surge.
We can confirm that the new Samsung S21 is vulnerable to the "Offline Attack" mode - and surprisingly, seems to have even less protection than the older S20 model.
For owners of the USBKill V4 Classic or the USBKill V3 - the "Online Attacks" would also appear to work on this model.
For more information, or to get your own USBKill V4: USBKill.com