When putting Debian Stretch onto an older computer which has a UEFI boot bios, I went into the bios, and disabled the UEFI boot security stuff, but still built a UEFI boot configuration when installing Debian:
- During the drive search process, select OK for the 'force UEFI' pop up question. Without this the EFI selection in the file system selector will not show.
- Select manual partitioning at the partitioning menu
- Partition table new drive with GPT
- Create first partition with 1MB and select 'BIOS Boot process'
- Create a second partition of about 100MB, and select the EFI process, which will mount on /boot/efi, and auto set the bootable flag
- Create a third partition of about 100MB, and select EXT3 or EXT4, and select /boot as a mount point, and optionally set it as read-only (will need to be changed to rw during upgrades and such, and any time initramfs changes are made)
- Create additional partitions as normal
- Proceed with installation process
- For some installations, I use a fast SDCard for basic boot operations. For that, near the end of the installation process, there is another UEFI pop up asking about forcing to removable media, with requires a manual selection of YES.