Comment 84 for bug 1863434

Same problem here. My computer is an Acer E1-571 with the latest firmware update.
Here the data sheet: https://www.acer.com/datasheets/2012/4876/E1-571/NX.M09ET.005.html

With Bionic, Grub 2.02 correctly recognise Windows 10 and show the Grub menu.
Also with Focal, Grub 2.04 correctly recognise Windows 10 but not show the Grub menu.

I've found 3 workaround:
1) Downgrade Grub 2.04 to 2.02 using the deb packages present in the Bionic repositories or upgrade to 2.06 from sources.
2) Enable the `console` mode (remove the "#" from `#GRUB_TERMINAL=console` in `/etc/defautl/grub`), but this disables graphics themes.
3) Disable Secure Boot and use `efibootmgr` to set the "grubx64.efi" boot entry as first.

With Secure Boot enabled, the boot is possible only via the "shimx64.efi" boot entry. If the boot is from this entry, the Grub menu is visible only in console mode. The same if Secure Boot is disabled, so the problem is not Secure Boot. The same downgrading Shim Signed to 1.37 version, from the Bionic repositories, so the problem is not Shim.

In Ubuntu Bionic (that use Grub 2.02, Shim Signed 1.37 and show the graphics Grub menu out of the box) I upgrade Shim Signed to 1.40, the Focal version, and the Grub menu is still showed in graphics mode, regardless of Secure Boot. This confirm the problem is not Shim or Secure Boot, but Grub 2.04 on Focal (and maybe Groovy and Hirsute).