@janfr – Open dispart and select the drive as per the guide, then:
DISKPART> clean
DiskPart has encountered an error: Access is denied.
See the System Event Log for more information.
DISKPART> convert gpt
DiskPart successfully converted the selected disk to GPT format.
DISKPART> create partition primary
DiskPart succeeded in creating the specified partition.
DISKPART> format quick fs=ntfs
100 percent completed
DiskPart successfully formatted the volume.
I just downloaded and flashed Endeavor OS to replicate your setup. Upon completion, I attempted to recover. I had to use an extra step, convert gpt, as it seems Endeavor uses a different partition table. Let me know if that works.