According to Ubuntu's community documentation,
[...] in a UEFI-mode installation, Ubuntu will not ask you where to install the boot loader. If it does, or if it complains about the lack of a BIOS Boot Partition, you've probably accidentally booted in BIOS/CSM/legacy mode.
However, when I tried installing Ubuntu Gnome 16.04 in the UEFI mode, it asked me to select a disk or a partition for the boot loader. I chose the /boot partition. I do not know if it really installed some "boot loader" to that partition, but it also created /EFI/ubuntu folder on the EFI system partition, and Ubuntu shows up in the UEFI boot menu. When I load Ubuntu, it mounts EFI system partition as /boot/EFI.
Is this an installer bug? If not, how does it agree with the documentation that I quoted?
P.S. This is one of a few anomalies I encountered in trying to set up a multi-boot system, I included more details in my another question.
As @alexey has already suggested in the comments (but I’m not allowed to comment), it indeed seems like a bug in installer that still persists. I could confirm it in the installer of Xubuntu 19.04. The documentation statement quoted above also still exists. I did double-check that legacy mode is disabled and the live medium was booting in UEFI mode. Expecting that it doesn’t have an effect, I left the choice of boot loader installation target at the disk root. The installation worked without issues. I did it on Dell Inspiron 11 3162 alongside Windows (select “something else”) where I was replacing Ubuntu 17.04 that was previously installed.
Partitioning dialogue in the installation process showing a drop-down menu for the boot loader installation device: