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You may simply try to boot the Garuda live USB and run Garuda Boot Repair if you have not done this yet.
You also may try this:
https://forum.garudalinux.org/t/grub-fails-after-update/78/3
This tutorials might help if the steps shown in the link above are not detailed enough. Boot the Garuda Live USB and follow the tutorial. I had bookmarked these because my problem about a year ago was solved by following these steps:
Chroot for EFI systems
https://discovery.endeavouros.com/system-rescue/arch-chroot-for-efi-uefi-systems/2021/03/
Repair non booting GRUB:
https://discovery.endeavouros.com/system-rescue/repair-a-non-booting-grub/2021/03/
Be sure to use the steps in the Repair GRUB on EFI/UEFI systems section!