What in the world? Your syslog says that grub-install tried to run efibootmgr, and it is not found. Can you run apt-cache policy efibootmgr and post the output?
What in the world? Your syslog says that grub-install tried to run efibootmgr, and it is not found. Can you run apt-cache policy efibootmgr and post the output?