On the flash drive there is an installed Linux Mint (not LiveCD, UEFI), in Windows 10 made from the DSK section, using the VirtualBox utility converted to VDI, connected as a hard disk, when loading VM writes
Fatal: No Bootable Medium Found. System Halted
connected LiveCD, made Update-Grub, did not help. How to configure such a system?
Try to enable UEFI in the virtual machine settings.