From the Debian stretch installation guide, I expected that the installer would install as UEFI. It states:
My system is a single boot environment with a single 1TB disk and has a Gigabyte H110M-S2H-CF motherboard with American Megatrends Inc. firmware which clearly states that "UEFI is supported", which is confirmed by the dmidecode output. The previous installation on this disk was fedora which installed as UEFI."3.6.3. Systems with UEFI firmware
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when booting debian-installer on a UEFI system with CSM because debian-installer checks whether it was started on a BIOS- or on a native UEFI system and installs the corresponding bootloader. Normally this simply works but there can be a problem in multi-boot environments."
I don't know whether there is a problem with the Debian installer, or a problem with the UEFI firmware or the user. I have read that not all UEFI technology is free of bugs. Despite the fact that the machine works without evident problems at present, my queries are: did I miss something in the installer to control installing as UEFI? And, does it matter at all on this single 1TB hard disk system, whether the MBR or UEFI is used?