After much fretting, I got a working solution. The solution would be to simple type in sudo mount /dev/sdx2 /boot/efi
before attempting to install grub.
A more detailed guide including Daniel's guide and some additions by me for adding drivers for Macs and Nvidia GPUs as well as useful generalisation to apply to any distribution of Linux :
https://docs.google.com/document/d/14PWThtbylgmqsnQbR8hUbgU6hfh55GJ9N1EOEEbrnzg/edit?usp=sharing
The document mentioned above is written with 3 purposes:
- Allow you to make your portable, full-fledged Linux install that will, ideally, work on any x86 PC that you wish to boot from.
- Achieve the 1st objective , ideally, on any distro.
- Allow a complete noob to follow instructions and links to achieve the 1st and 2nd objective.