Installed Garuda on external hdd. Won't boot in any other system then the one it was installed on

Issues & Assistance Unsupported Software (AUR & Other)
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You could create on the external disk a 300MB partition formatted FAT32.
From a live USB, chroot into the system on the external drive.
To chroot, you can use the tool in the live ISO or this tutorial:

From inside chroot mount the newly created partition to /boot/efi and execute

grub-install --target=x86_64-efi --efi-directory=/boot/efi --bootloader-id=garuda --no-nvram --removable
update-grub
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