[Assist] Newbie trying to do LUKS on software RAID

[amuza]

Hello!

I am new to both Parabola, to this forum and to Arch world!

I am not an expert, but an average user of a Debian-based distro who 
wanted to try Parabola for a long time.

And I am not either an expert on partitions, RAID or luks, but I have a 
3-disk computer and that is where I want to install Parabola, having the 
disks luks-encrypted and having a RAID1 mirror. The system would go on 
Raid1 and non-critical data on the non-raid third disk.

Fortunately, the setup I want to achieve is step-by-step explained in 
this guide:
https://wiki.archlinux.org/title/Dm-crypt/Encrypting_an_entire_system#LUKS_on_software_RAID

I am following every step on that guide. Everything was fine until I 
reached the "Configuring GRUB" section.

I did
vi /etc/default/grub
I found an empty file and added what the guide says.

Then, when trying to run the grub-install commands on the guide, I found 
grub was not installed.
I searched on the Internet on how to install grub and did it.

But now, when trying to run those grub-install commands, I get the 
following:

root at parabolaiso / # grub-install --target=i386-pc /dev/sda
Installing for i386-pc platform.
grub-install: error: failed to get canonical path of 'airootfs'.
1 root at parabolaiso / # grub-install --target=i386-pc /dev/sdb
Installing for i386-pc platform.
grub-install: error: failed to get canonical path of 'airootfs'.
1 root at parabolaiso / # grub-install --target=x86_64-efi 
--efi-directory=/efi --bootloader-id=GRUB
Installing for x86_64-efi platform.
grub-install: error: failed to get canonical path of '/efi'.

How could I solve that error?

Thank you!