Ubuntu on 32-bit UEFI (only) based tablet pc

So far you're doing everything right, you just need to modify the USB so that it will boot on a 32-bit UEFI only system.

While Windows is running or on another machine, insert the USB and find a directory called /EFI/BOOT. This needs to contain a bootia32.efi file (even if there is one there already it might not be one that works - last time I found one but had to replace it)

click here to download a bootia32.efi file that worked for me recently.

Drop this file into the right place (remember all the file and directory names are case sensitive) and your USB should boot, given appropriate UEFI settings (secure boot off, USB first or selected in boot menu)