Wish I could suggest more. Maybe there’ll be someone along with a similar setup or who can advise.
EDIT: roughly searched ‘bios/grub/latitude’ in the Arch Wiki and tbh no idea if this next bit will help, but incase it does …
" In addition to the UEFI firmware workaround (without which GRUB isn’t launched), the Dell Latitude seems to require to have the EFI system partition mounted on /boot
. When ESP is mounted on /efi
, GRUB fails to find the configuration files and launches the rescue console."
Not sure exactly how this would work on your system, but if all else fails, get the image from the Galleon thread https://forum.endeavouros.com/t/endeavour-galleon-wallpaper/2332/15 , put it in Pictures and e.g. name it GRUB.png, then, in /etc/default/grub do the following:
Uncomment one of them for the gfx desired, a image background or a gfxtheme
GRUB_BACKGROUND="/home/your username/Pictures/GRUB.png"
#GRUB_THEME="/path/to/gfxtheme"
Then refresh grub.
I can bet you already know that though!