Manjaro enjoys me. 
Thank you all for your Work and Infos in this Forum.
It helped me a lot - since now I was a “silent Reader”. If post is at wrong place, feel free to split to a new topic. The Problem I got solved, the Description may help others.
Usually all the Updates went without attracting Attention, which is fine.
This Time I tried to push grub/Bootloader too - as suggested:
sudo grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=manjaro --recheck
sudo grub-mkconfig -o /boot/grub/grub.cfg
shortly after giving the Password to Luks Encryption:
Error symbol "grub-is-cli-auth-need-auth" not found
Cause: System here: Luks/encrypted, btrfs with Subvolumes
A Downgrade after chrooting gave...
Error symbol grub_is_shimlock_enabled not found
Booting with supergrubdisk or Ventoy (Browse/Boot Files In Local Disk) was for me easier then chrooting ino btrfs - also it finds most existing Bootloader on your Disk
You may first backup your /boot/grub/grub.cfg due to uuid`s of encrypted Partitions inside
sudo grub-install ... --recheck
seems not to notice Encryption on GPT2, writes GPT1 in my UEFI-Bootmenu
and does not update the generic EFI-Bootloader in /boot/efi/EFI/boot/bootx64.efi
sudo tree /boot/efi
# should give:
/boot/efi
└── EFI
├── boot
│ └── bootx64.efi # generic, fallback EFI-Bootloader
└── Manjaro
└── grubx64.efi
Sync the fallback EFI-Loader: forum.manjaro.org root-tip-how-to-primer-on-handling-a-grub-package-update/154003
One thing to mention is the flag –removable of grub-install - explained well in post #28 at archlinux.org pid=2157953#p2157953
better Fix:
sudo pacman -Syu grub
sudo grub-install --removable
sudo grub-mkconfig -o /boot/grub/grub.cfg