UEFI BIOS offers advantages over legacy versions of BIOS, it possesses many new features and advantages that cannot be achieved through the traditional BIOS and it is aimed to completely replace the BIOS in the future. Besides, Windows 11 only supports UEFI boot mode, so if you want to upgrade to Windows 11, you need to change the boot mode from Legacy to UEFI.
To change boot mode
1. Press F2 or other shortcuts continuously when prompted to enter BIOS menu. From the BIOS Main menu screen, select Boot.
2. From the Boot screen, select UEFI/BIOS Boot Mode, and press Enter. Then the UEFI/BIOS Boot Mode dialog box appears.
3. Use the up and down arrows to select Legacy or UEFI, and then press Enter.
4. To save the changes and exit the screen, press F10.
For newer motherboards, the setup is simpler. Please make sure that UEFI support is turned on (Launch CSM enabled) then it will work.