Boot failing device not found

General system
9

I see only this is legacy system or CSM install ?
First thing to try is to boot into rescue ISO (installer) and arch-chroot as shown on the bottom of the wiki for BTRFS and encryption… (have in mind that you do not have the esp fat32 partition)
https://discovery.endeavouros.com/system-rescue/arch-chroot/2022/12/

When inside the chroot:

  1. update installed system pacman -Syu
  2. regenerate kernel images according to your install latest ISO used dracut molder install or changed Mkinitcpio: mkinitcpio -P
    Dracut: dracut-rebuild
  3. reinstall grub files: grub-install /dev/sda and regen grub.cfg: grub-mkconfig -o /boot/grub/grub.cfg
    logout the chroot and reboot into installed system (if lucky)