Hi,

I have been recently helping a friend to try Debian installation in an
ASUS Transformer T100. It is a tablet coupled to a detachable keyboard
having a hard disk. It has a 64bit Intel processor, but a 32 bit UEFI
and no legacy mode, and this is the first problem we found.

Searching the web about this issue, I found that this problem is not
only in this particular box, but also appears in other boxes, having
Intel Bay Trail 64bit processor, but 32bit UEFI with no legacy
support,

https://bugs.launchpad.net/ubuntu/+source/grub2/+bug/1341944

Quoting from that Ubuntu bug report