Cannot boot a USB HDD on iMac

[admin]

Which partition scheme did you choose when creating the WTG? Mac computers are UEFI-based computers, so you should choose “MBR for BIOS and UEFI” or “GPT for UEFI” partitioning scheme when creating WTG. For more information, please refer to:
https://www.easyuefi.com/wintousb/resour...n-mac.html