A normal USB cable is sufficient. However, the SSD must be formatted with Fat. If it is not, it cannot be read by smartphones. Here, someone shows how it works:
https://youtu.be/b1sXBob_uXY
I don't understand the "currentless"...
The SSD has/can only have USB.
The Raspberry has/can only have USB.
So the connection can only be made via USB.
In this regard, it is best to contact our customer service directly at https://helpcenter.galaxus.ch/hc/de/requests/new. Then your request can be checked individually.