What if you try the manual procedure:
sudo mkdir -p /mnt/broken
sudo mount /dev/sda6 /mnt/broken
sudo garuda-chroot /mnt/broken/@
Then into the chroot:
mount /dev/sda1 /boot/efi
grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=garuda --recheck
update-grub