Good afternoon,
I was following the explanation to install Grub as per the web page
https://www.nutyx.org/en/grub-install instructions. The first steps should be:
1/ When booting the ISO, choose the Install option (not the Live option)
2/ Select the Language
2/ A new screen will pop-up with three options: Help, Install, Advanced. Chose Advanced.
3/ Chose the option to install GRUB
3/ You can resume the installation as described on the web page then.