Bios finds efi even it's not mounted and probably passes where it is to Linux, but grub installer not take the info into account.
I have the only linux system.

I'm not sure if this applies to your case, but I also had a black screen due to an unmounted EFI partition.

It was a message that system may no boot:

Setting up grub-efi-amd64 (2.12-9) ...
Installing for x86_64-efi platform.
grub-install: error: cannot find EFI directory.
Failed: grub-install --target=x86_64-efi  
WARNING: Bootloader is not properly installed, system may not be bootable
Generating grub configuration file ...

I used https://www.system-rescue.org/Installin … ory-stick/ that able to boot system with wrong efi, then mount
mount /dev/sda? /boot/efi
and ran update-grub

I.e., before the final step of the system installation, one should check  whether efi is mounted.