How do I use Timeshift/btrfs to permanently restore to a previous snapshot?

Support Software & Applications
38

If that does not work, then use manjaro-chroot on Live USB to fix Grub.

# mount -t btrfs /dev/nvme0n1p2 /mnt
# manjaro-chroot /mnt/@
# mount /boot/efi
# update-grub

Then check what is the output cat /boot/grub/grub.cfg