Arranque UEFI

Hola he comprado un portátil que por lo visto solo permite arranque UEFI.

Cuando instalo Trisquel 8 me tira el siguiente mensaje:

No se pudo instalar el paquete "GRUB-AMD 64" en "/TARGET/". El sistema instalado no podrá arrancar sin el cargador de arranque de grub.

me pasa lo mismo tanto instalando desde un USB como desde un DVD.

El particionado es gpt y la partición efi esta marcada con los flags boot y esp.

La única solución que he encontrado en internet que parece posible es:

https://askubuntu.com/questions/1028921/the-grub-efi-amd64-signed-package-failed-to-install-into-target-during-ins

"""

Let's suppose you installed Ubuntu in /dev/sdXY partition, and an already existed ESP is in /dev/sdXZ partition,
on the hard drive /dev/sdX. Open a terminal and execute these commands :

$ sudo mount /dev/sda5 /mnt
$ sudo mount /dev/sda2 /mnt/efi
$ for i in /dev /dev/pts /proc /sys /run; do sudo mount -B $i /mnt$i; done
(Now, if you customized Ubuntu installation by dividing some directories up into different partitions (eg. '/boot', '/opt', etc.),
you should mount them too under `/mnt` directory. You may refer to `/mnt/etc/fstab` file to remember what you did on the installed Ubuntu system)
$ sudo chroot /mnt

Reinstall grub2 with the right EFI version

Once you chroot successfully into your installed Ubuntu system, make sure to (re)install the right grub-efi-* package for your PC architecture :

# apt-get install --reinstall grub-efi-x86_64 (the one I used for Intel i5 CPU)

or

# apt-get install --reinstall grub-efi-amd64

or

# apt-get install --reinstall grub-efi-ia32, etc... You can get the list of available packages with # apt-cache search ^grub-efi

Finally, to install grub2 into your drive:

# grub-install --boot-directory=/boot --bootloader-id=ubuntu-fix --target=x86_64-efi --efi-directory=/efi
# update-grub

Please note the --target=x86_64-efi can be different depending on your system (eg. i386-pc by default, maybe amd64-efi, etc.). Check # grub-install --help for more info.
Exit chroot, unbind/unmount safely directories & reboot

Exit chroot with Ctrl+D or # exit

Unmount safely and reboot :

$ for i in /sys /proc /dev/pts /dev; do sudo umount /mnt$i; done
$ sudo umount /mnt/efi
(Unmount any other customized partitions, if you had any)
$ sudo umount /mnt
$ sudo reboot

Ubuntu should now boot normally.

"""

pero al intentar montar la partición efi me dice que no existe el punto de montaje:

trisquel@trisquel:~/Desktop$ sudo mount /dev/sda2 /mnt/efi
mount: mount point /mnt/efi does not exist

¿Alguna sugerencia?

Gracias.