@steve6375
I did a test with another 16GB FAT32 flash drive and it works now
efi\boot\bootx64.efi -> GRUB4DOS UEFI
efi\grub\menu.lst
timeout 5 default 0 title Debian 9 (vmlinuz, initrd.img) kernel /images/deb9/vmlinuz boot=live live-media-path=/images/deb9/live/ config username=root initrd /images/deb9/initrd.img
images\deb9\live\filesystem.squashfs
images\deb9\initrd.img and vmlinuz
I don't know why, but with a Kingston 1GB SD card in a USB 2.0 reader, GRUB4DOS UEFI does not work.
The same SD card in the USB reader works without any problems in UEFI Shell