It's FOSS - https://itsfoss.com/check-uefi-or-bios/
Brief: A quick tutorial to tell you if your system uses the modern UEFI or the legacy BIOS. Instructions for both Windows and Linux have been provided.
When you are trying to dual boot Linux with Windows, you would want to know if you have UEFI or BIOS boot mode on your system. It helps you decide in partition making for installing Linux.
UEFI or Unified Extensible Firmware Interface was designed to overcome some of the