J'ai également tenté avec boot-repair, sans succès :/
Voici le résultat :
An error occurred during the repair.
Please write on a paper the following URL:
http://paste.ubuntu.com/p/39XTXsYrnr/
In case you still experience boot problem, indicate this URL to:
boot.repair@gmail.com
Locked-ESP detected. You may want to retry after creating a /boot/efi partition (FAT32, 100MB~250MB, start of the disk, boot flag). This can be performed via tools such as gParted. Then select this partition via the [Separate /boot/efi partition:] option of [Boot Repair].
Le lien du rapport :
http://paste.ubuntu.com/p/39XTXsYrnr/