It was a broken ssd harddisk (the western digital sn850, WDS200T1X0E-00AFY0), which probably hadn’t yet the latest firmware. The disk wasn’t recognized by any system any more.
As guided by the framework team, I first removed all expansion card, the ram sticks and the ssd hard disk. After that, I made a mainboard hard reset and plugged in the ram sticks, the ssd hard disk and the expansion cards again. After reinserting the ssd hard disk, the system would work any more.
I now get a replacement disk from framework.