When installing Ubuntu using the “Something else” option, a "Device for boot loader installation" option is presented.
I understand that, when installing Ubuntu in BIOS mode, the "Device for boot loader installation" option controls where (within which boot sector) portions of GRUB will be installed.
But, if I understand correctly, when installing Ubuntu in UEFI mode, much of GRUB is installed within the EFI System Partition (ESP), with the remainder being installed within the Ubuntu file system. That is, no portion of GRUB is installed into a boot sector when installing Ubuntu in UEFI mode. (Please let me know if I am wrong regarding where GRUB is installed when installing Ubuntu in UEFI mode.)
QUESTION: When installing Ubuntu in UEFI mode, what (if anything) is installed at the location specified using the "Device for boot loader installation" option?
I asked a Canonical employee who has knowledge of the subject, and that employee replied as follows: