Re: GPT

La partition EFI est absente de sdb donc du ssd.
Et vu le message sur sda j'ai comme l'impression que l'installateur n'a pas fait son job correctement

sda1: __________________________________________________________________________
 File system: iso9660
 Boot sector type: Unknown
 Boot sector info: 
 Mounting failed: mount: /mnt/BootInfo/sda1: /dev/sda1 already mounted or mount point busy.
sda2: __________________________________________________________________________
 File system: vfat
 Boot sector type: FAT16
 Boot sector info: According to the info in the boot sector, sda2 starts 
 at sector 0. But according to the info from fdisk, 
 sda2 starts at sector 2879436. According to the info 
 in the boot sector, sda2 has 0 sectors.
 Mounting failed: mount: /mnt/BootInfo/sda1: /dev/sda1 already mounted or mount point busy.
mount: /mnt/BootInfo/sda2: /dev/sda2 already mounted or mount point busy.
sdb1: __________________________________________________________________________
 File system: LVM2_member
 Boot sector type: -
 Boot sector info: 
ubuntu-vg-root: ________________________________________________________________
 File system: ext4
 Boot sector type: -
 Boot sector info: 
 Operating System: Ubuntu Bionic Beaver (development branch)
 Boot files: /boot/grub/grub.cfg /etc/fstab 
 /boot/grub/i386-pc/core.img
ubuntu-vg-swap_1: ______________________________________________________________
 File system: swap
 Boot sector type: -
 Boot sector info: 

Plus précisément la partie :

According to the info in the boot sector, sda2 starts
at sector 0. But according to the info from fdisk,
sda2 starts at sector 2879436. According to the info
in the boot sector, sda2 has 0 sectors.

Ca sent le truc qui a mal tourné. Puis comme dit à moins que tu démarres en mode legacy tu as besoin de cette partition sur sdb.