dual boot – `chainloader bootmgfw.efi` does not load Windows

I have installed Ubuntu alongside with Windows 10, and they are on different disks. Since the disk containing Windows does not have a UEFI partition and uses C:/EFI/Microsoft/Boot/bootmgfw.efi to load Windows instead, grub does not recognize the Windows bootloader.

If I boot from Ubuntu install USB and enter the grub command line, by running the following commands I can start Windows successfully:

chainloader (hd1,msdos1)/EFI/Microsoft/Boot/bootmgfw.efi
boot

However, if I enter the grub command line of the installed Ubuntu on disk, when I run:

chainloader (hd1,msdos1)/EFI/Microsoft/Boot/bootmgfw.efi

it print Error: invalid signature. If I add --force option to chainloader and then boot, the screen goes blank and windows does not start up.

Can anyone give some suggestions on how to boot Windows from Ubuntu grub?

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