Qui c'è la guida ufficiale per l'installazione UEFI, se non l'avevi già vista ( hai disabilitato secure boot ? ) .
Il pc che dici comunque non ha un SSD ma una eMMC ... non sò quanti pc supportino il boot da SD ( oltre al fatto che avrebbe delle prestazioni lentissime , credo ) , ho trovato questo :
The internal SD card reader is not a bootable device.
It's connected to PCI-E bus (for better performance I think, it showed much higher speed than average external ones), which means BIOS could not access it like commom internal/USB drives (mSATA is a new category but basically internal drive with a new interface).
Even the BIOS could recognize it, the on-card software needs driver for the card reader, or they will simply fail to load themselves because they cannot access their own media.
If you have to use a bootable SD, use with a USB port card reader. The Mass Storage Device standard devices are commonly bootable.