You’re definitely not the only one who’s struggled with Immich on ZimaOS, especially when using USB drives. Version 1.4.3 had a few quirks with how it handled external disks, and that often caused the setup to fail when trying to store data or databases on them.
The good news is that ZimaOS 1.5.0 is out now, and it includes major improvements to external drive handling. Once you update, Immich usually installs and runs smoothly without any extra tweaks.