I just found another topic which is related to the issue we have:
Maybe this leads to a solution…
For info: at step 3 (Write the image to NVME drive. I used an USB to NVME adapter): it is also possible to burn the “Radxa” Debian on a uSD or eMMC card, copy a image onto this system and DD it to the nvme SSD. So there’s no need to buy additional hardware.
Currenty I have a nvme SSD with a written /boot partition which I can’t delete, so my progress is at a halt the comming days.