Today one of my linux servers did not boot. Instead there was a grub uefi shell. Typing the help command listed a bunch of commands in dark blue on a dark grey. Not easy to read. Trying to use the gui did not solve the problem. Resetting the config did also not help. Some forum posts said to create a symlink to the efi file. My issue was that /boot/efi is a separate partion due btrfs on the my system.
What did work was using the command line to add the efi again.
bcfg boot add 0 fs0:\EFI\debian\grubx64.efi "Debian"
However writing in english mode on a german style keyboard is often “times of wonder”. Use # ( hash) for the backslash and ä for the quotes. I still wonder why I have to use a backslash on a linux system…