fbx64.efi hangs after Debian 10.10 shim update

[Pascal Hambourg <pascal@plouf.fr.eu.org>]

Hello,

I have Debian 10 amd64 installed on an old HP EliteBook 2570p. The UEFI 
firmware seems to ignore the EFI boot entries and only be able to boot 
from the removable device path EFI\BOOT\BOOTX64.EFI by default. After 
each boot a new "debian" EFI boot entry was added, so I removed 
/boot/efi/EFI/BOOT/fbx64.efi to avoid this. So far so good.

After the latest shim update which ran grub-install and installed the 
new /boot/efi/EFI/BOOT/fbx64.efi, UEFI boot hangs with no error message, 
only the HP logo, and GRUB does not show up.

Using "Boot from EFI file" in the firmware boot menu, it appears that :
- grubx64.efi (from either EFI\debian or EFI\BOOT) works
- shimx64.efi (from EFI\debian) works
- BOOTX64.efi (from EFI\BOOT) hangs
- fbx64.efi (from either EFI\debian or EFI\BOOT) hangs

So as a workaround, I removed /boot/efi/EFI/BOOT/fbx64.efi again.