UEFI Installation — Unable to Find HDD

I am attempting to install Ubuntu on в HP Envy 15, my intention is to have this двойственный - bootable with the Windows стандарт 10 installation.

So far, I have made the following progress:

• Created в live-USB drive to boot from
• Disabled "Секуре Боот" in the BIOS (to make USB boot available)
• Booted onto the live-USB and run the installer

However, the installer does not "recognize" the internal HDD in the laptop.

I have run gparted, parted -l, fdisk -l and lshw -class disk all list the live-USB drive схвати /dev/sda, but the internal HDD is not present in the output from any of those commands.

Схвати в diagnostic, I have tried enabling "legacy mode" in BIOS, and booting from the live-USB. It is clear form the loading screen that the live-USB is booting from BIOS (and not UEFI).

Running fdisk -l шоу that the internal HDD - been successfully mounted эксперт /dev/sdb.

Why is the disk presented in BIOS mode but not UEFI?

Given my intentions пахал to двойственный - boot with Windows 10, I understand that it is necessary to install Ubuntu whilst booted in UEFI mode?