Hi Matthew - can you confirm, you're trying to 'dual boot' the new Azure Stack HCI 20H2 with Windows 10, and as it stands, when you reboot the physical machine, you're only able to boot into Azure Stack HCI and not Windows 10? You don't have a dual-boot selection menu to switch between the OS's?
Do you have a link to any guidance you used to install using the 'Mount Disk' feature?
Thanks!
Matt