Supergrub2disk helped me to have the choice at startup

[hub . lombard]

Hi Guix :)

A few days ago, I managed to install GuixSD 0.16 next to debian testing on a 
Packard Bell 'EasyNote TE' laptop.
At reboot, Grub only offers GuixSD.
To have the choice at startup, I used the 'supergrub2disk' that I downloaded 
and put on a USB key, positioned as the first boot device.
SuperGRUB2disk gives me the choice between GuixSD and debian, and I can start 
either one without any problem.

For now, I keep the USB key inserted in the computer and everything is fine, 
having nevertheless planned to address the problem of the restoration of GRUB. 

Would someone have a track that would enlighten me a bit?

The GRUB originally installed on debian was on /dev/sda1

I installed GuixSD on /dev/sda6 (my-root). As a result, the new GRUB is also on 
/dev/sda6. In 'config.scm', the bootloader points to /dev/sda

(bootloader (grub-configuration (target "/dev/sda")))
(file-systems (cons (file-system
                      (device "my-root")
                      (title 'label)
                      (mount-point "/")
                      (type "ext4"))
                    %base-file-systems))

Apart from this issue, I will focus on the importance of supergrub2disk in the 
case of an installation, especially for an end user like me.

The first time it was after the installation of GuixSD 0.14 on my other laptop, 
it had worked as well and GRUB had been easy to restore.

https://www.supergrubdisk.org/category/download/supergrub2diskdownload/

Hoping it could be useful to other people ...

Thank you in advance for your advice

Hubert