Firstly I complety know my hard drive password and I confirmed that it works opening it witha a Live USB, but When I try to type the password in the password prompt it never gets it right.
I am sure way beyound any reasonable doubt that is a problem with keyboard layout configuration, the point is that my computer has a American layout keyboard and I configured Neo2 at installation time but for what I remember Grub has little to no hability to change layout, but because grub is no the one asking the question of what is my password but some liveramfs I am not sure what layout is being used.
Another thing to watch out for (particularly if you are using a laptop) is that NumLock can sometimes be “on” without you knowing it. My laptop has no way of indicating this, so it caused me no end of trouble until I took out the piece of felt that was there to protect the screen while the laptop was closed. (This would toggle the NumLock sometimes–without my knowing about it.) So now I have a scuffed-up screen but at least I can log in.
the passphrase is asked after grub, during initramfs. My french layout was recognized correctly out of the box because I chose it during installation.
I’m not sure, but I think this is defined through systemd: using localectl set-keymap keymap (you may need to try localectl set-keymap --no-convert keymap if you don’t want a variant approximation).
Possible workaround: press e on grub menu then type your password anywhere in it until you identify all the keys. Then delete it and exit grub continuing to password prompt now typing properly identified keys.