How to test whether Windows 10 was installed with UEFI?

I need to decide whether it is more straightforward to create a bootable Ubuntu drive in UEFI or standard BIOS. I do not want to create or install it through any more ambiguous route than necessary because I have experience with accidentally installing one on the other's environment.

Open the System Information Utility (Win Key + "R" > "msinfo32" > OK)

In system summary, look for "BIOS MODE".

Alternatively, check Disk manager. If you have a partition on your disk for "EFI system partition" then you are using UEFI. If you only have system reserved and C:, its probably BIOS.

Hope one of these helps

You can also use Windows Panther directory logs:

type C:\Windows\Panther\setupact.log|find /i "Detected boot environment"

Extracted from: http://www.sysadmit.com/2017/04/windows-uefi-o-legacy-bios.html