Just some tips for people trying to get Pi4 booting directly from SSD.
I am using here the newest image file v1.6-alpha dated on 30July2020.
Generally You can follow these updated instructions
The *.elf and *.dat files provided by the Openhabian v1.6-alpha image are too old, and your Pi4 won´t boot with these files. I think these are dated on 17May2020 and won´t work!
Solution is simple just replace these 16 *.elf and *.dat files on your boot partition with the file versions from 25May2020. I just extracted the files from an raspian OS file dating on 25May2020 (e.g. github)
The only trouble I was facing not all USB3 adapters will work here!
The first adapter I tried wasn´t working now I just bought a very cheap startech USB3 adapter
and it works with my Kingston 960GB/SSD perfectly without extra power supply.
This is what I was searching for:-)
One wish, can we please update these elf/dat files for the provided openhabian image file?