[Renate]

900e is system crash. You can't do anything from there.
You want 9008, which is EDL mode.

Flashing payload.bin is exactly the wrong thing to do, especially to sector 0.
You've wiped out the MBR & GPT of LUN 0 or which LUN?

You should be able to restore from the backup GPT (but not directly).
I forget how they are mirrored.

AFAIK, there are none of those XML files for Onyx available (although they could be created).

Don't go crazy flashing stuff. All that rawprogram and patch stuff is really designed for factory flashing of blank devices.

Edit: The GPT entries from backup will be correct.
The GPT headers will need current_lba & backup_lba swapped, entries_lba changed and header_crc recalculated.