je colle ci-dessous le contenu du Boot-info dont tu as donné le lien :

boot-info-4ppa125                                              [20201013_1110]

============================== Boot Info Summary ===============================

 => Grub2 (v2.00) is installed in the MBR of /dev/sda and looks at sector 1 of 
    the same hard drive for core.img. core.img is at this location and looks 
    for /boot/grub. It also embeds following components:
    
    modules
    ---------------------------------------------------------------------------
    fshelp ext2 part_msdos biosdisk search_fs_uuid
    ---------------------------------------------------------------------------
    
    config script
    ---------------------------------------------------------------------------
    search.fs_uuid 210e2852-0204-4930-aa53-5a1a64196bfa root hd0,msdos1 
    set prefix=($root)'/boot/grub'
    
    ---------------------------------------------------------------------------
 => Grub2 (v2.00) is installed in the MBR of /dev/sdb and looks at sector 1 of 
    the same hard drive for core.img. core.img is at this location and looks 
    for (,msdos1)/boot/grub. It also embeds following components:
    
    modules
    ---------------------------------------------------------------------------
    fshelp ext2 part_msdos biosdisk
    ---------------------------------------------------------------------------

sda1: __________________________________________________________________________

    File system:       ext4
    Boot sector type:  -
    Boot sector info: 
    Operating System:  
    Boot files:        

sdb1: __________________________________________________________________________

    File system:       ext4
    Boot sector type:  -
    Boot sector info: 
    Operating System:  Ubuntu 20.04.1 LTS
    Boot files:        /boot/grub/grub.cfg /etc/fstab /etc/default/grub 
                       /boot/grub/i386-pc/core.img


================================ 1 OS detected =================================

OS#1:   L'OS actuellement utilisÃ© - Ubuntu 20.04.1 LTS CurrentSession on sdb1

============================ Architecture/Host Info ============================

CPU architecture: 64-bit
BOOT_IMAGE of the installed session in use:
/boot/vmlinuz-5.4.0-48-generic root=UUID=915f5484-1c63-4303-b25c-3b703f5e1575 ro quiet splash vt.handoff=7


===================================== UEFI =====================================

This installed-session is not in EFI-mode.



============================= Drive/Partition Info =============================

Disks info: ____________________________________________________________________

sdb	: notGPT,	no-BIOSboot,	has-noESP, 	not-usb,	not-mmc, has-os,	2048 sectors * 512 bytes
sda	: notGPT,	no-BIOSboot,	has-noESP, 	not-usb,	not-mmc, no-os,	2048 sectors * 512 bytes

Partitions info (1/3): _________________________________________________________

sdb1	: is-os,	64, apt-get,	grub-pc ,	grub2,	grub-install,	grubenv-ok,	update-grub,	farbios
sda1	: no-os,	32, nopakmgr,	no-docgrub,	nogrub,	nogrubinstall,	no-grubenv,	noupdategrub,	farbios

Partitions info (2/3): _________________________________________________________

sdb1	: isnotESP,	fstab-without-efi,	no-nt,	no-winload,	no-recov-nor-hid,	no-bmgr,	notwinboot
sda1	: isnotESP,	part-has-no-fstab,	no-nt,	no-winload,	no-recov-nor-hid,	no-bmgr,	notwinboot

Partitions info (3/3): _________________________________________________________

sdb1	: not-sepboot,	with-boot,	fstab-without-boot,	not-sep-usr,	with--usr,	fstab-without-usr,	std-grub.d,	sdb
sda1	: maybesepboot,	no-boot,	part-has-no-fstab,	not-sep-usr,	no---usr,	part-has-no-fstab,	std-grub.d,	sda

fdisk -l (filtered): ___________________________________________________________

Disk sda: 1.84 TiB, 2000398934016 bytes, 3907029168 sectors
Disk identifier: 0x6c0c0c8d
      Boot Start        End    Sectors  Size Id Type
sda1        2048 3907029167 3907027120  1.8T 83 Linux
Disk sdb: 149.5 GiB, 160041885696 bytes, 312581808 sectors
Disk identifier: 0x7f8733b8
      Boot Start       End   Sectors   Size Id Type
sdb1  *     2048 312580095 312578048 149.1G 83 Linux

parted -lm (filtered): _________________________________________________________

sda:2000GB:scsi:512:4096:msdos:ATA WDC WD20EZRX-00D:;
1:1049kB:2000GB:2000GB:ext4::;
sdb:160GB:scsi:512:512:msdos:ATA ST3160215AS:;
1:1049kB:160GB:160GB:ext4::boot;

blkid (filtered): ______________________________________________________________

NAME   FSTYPE   UUID                                 PARTUUID                             LABEL  PARTLABEL
sda                                                                                              
â””â”€sda1 ext4     0753f5a3-553e-4693-a7a9-11531921deb1 6c0c0c8d-01                          divers 
sdb                                                                                              
â””â”€sdb1 ext4     915f5484-1c63-4303-b25c-3b703f5e1575 7f8733b8-01                                 

df (filtered): _________________________________________________________________

       Avail Use% Mounted on
sda1     1.3T  24% /media/asocial/divers1
sdb1   108.2G  21% /

Mount options: __________________________________________________________________

sda1   rw,nosuid,nodev,relatime
sdb1   rw,relatime,errors=remount-ro

====================== sdb1/boot/grub/grub.cfg (filtered) ======================

Ubuntu   915f5484-1c63-4303-b25c-3b703f5e1575
Ubuntu, avec Linux 5.4.0-48-generic   915f5484-1c63-4303-b25c-3b703f5e1575
Ubuntu, avec Linux 4.15.0-118-generic   915f5484-1c63-4303-b25c-3b703f5e1575
### END /etc/grub.d/30_os-prober ###
### END /etc/grub.d/30_uefi-firmware ###

========================== sdb1/etc/fstab (filtered) ===========================

# <file system> <mount point>   <type>  <options>       <dump>  <pass>
# / was on /dev/sda1 during installation
UUID=915f5484-1c63-4303-b25c-3b703f5e1575 /               ext4    errors=remount-ro 0       1
/swapfile                                 none            swap    sw              0       0

======================= sdb1/etc/default/grub (filtered) =======================

GRUB_DEFAULT=0
GRUB_TIMEOUT_STYLE=hidden
GRUB_TIMEOUT=10
GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
GRUB_CMDLINE_LINUX=""

==================== sdb1: Location of files loaded by Grub ====================

           GiB - GB             File                                 Fragment(s)
  88.718944550 = 95.261241344   boot/grub/grub.cfg                             2
  88.687412262 = 95.227383808   boot/grub/i386-pc/core.img                     1
  34.566539764 = 37.115539456   boot/vmlinuz                                   1
   4.313472748 = 4.631556096    boot/vmlinuz-4.15.0-118-generic                2
  34.566539764 = 37.115539456   boot/vmlinuz-5.4.0-48-generic                  1
   4.313472748 = 4.631556096    boot/vmlinuz.old                               2
   4.313472748 = 4.631556096    vmlinuz                                        2
  25.436225891 = 27.311939584   boot/initrd.img                                2
  35.268966675 = 37.869764608   boot/initrd.img-4.15.0-118-generic             3
  25.436225891 = 27.311939584   boot/initrd.img-5.4.0-48-generic               2
  35.268966675 = 37.869764608   boot/initrd.img.old                            3
  35.268966675 = 37.869764608   initrd.img                                     3

===================== sdb1: ls -l /etc/grub.d/ (filtered) ======================

-rwxr-xr-x 1 root root 17622 sep  8 12:24 10_linux
-rwxr-xr-x 1 root root 42359 sep  8 12:24 10_linux_zfs
-rwxr-xr-x 1 root root 12894 sep  8 12:24 20_linux_xen
-rwxr-xr-x 1 root root 12059 jui 17  2018 30_os-prober
-rwxr-xr-x 1 root root  1424 sep  8 12:24 30_uefi-firmware
-rwxr-xr-x 1 root root   214 jui 17  2018 40_custom
-rwxr-xr-x 1 root root   216 jui 17  2018 41_custom


========= Devices which don't seem to have a corresponding hard drive ==========

sdc sdd sde sdf 

Suggested repair: ______________________________________________________________

The default repair of the Boot-Repair utility would reinstall the grub2 of
sdb1 into the MBRs of all disks (except live-disks and removable disks without OS).
Additional repair would be performed: unhide-bootmenu-10s      

Final advice in case of suggested repair: ______________________________________


Please do not forget to make your BIOS boot on sdb (ATA ST3160215AS) disk!

On y voit :

df (filtered): _________________________________________________________________

       Avail Use% Mounted on
sda1     1.3T  24% /media/asocial/divers1
sdb1   108.2G  21% /

Et si je cherche /media/asocial/divers1 dans ton journal.txt; je trouve cet extrait :

-- L'unité (unit) udisks2.service a terminé son démarrage, avec le résultat done.
oct 13 06:49:17 asocial-desktop udisksd[744]: Acquired the name org.freedesktop.UDisks2 on the system message bus
oct 13 06:49:17 asocial-desktop udisksd[744]: mountpoint /media/asocial/divers1 is invalid, cannot recover the canonical path 
oct 13 06:49:17 asocial-desktop udisksd[744]: Cleaning up mount point /media/asocial/divers1 (device 8:1 is not mounted)

La mention "mountpoint /media/asocial/divers1 is invalid" me parait bizarre mais c'est peut-être normal. EDIT : ben oui, c'est normal. Il existe une directorie "divers" qui a été créée dans /media/asocial/ probablement par toi (il y a peut-être très longtemps). A présent, quand tu demandes le montage de sda1, comme cette directorie "divers" est réservée, Ubuntu fait le montage dans "divers1". Au redémarrage suivant, cette directorie "divers1" est supprimée (d'où la mention "Cleaning up mount point /media/asocial/divers1"). Par contre la directorie "divers" n'est jamais supprimée.