neufbox6V: openwrt 23 on it

hello

im trying since few hours to put the openwrt on neufbox6V, which is supposed as well supported by openwrt
i block on those things, as using tftp well but image looks like to be rejected :

Illegal whole flash image                                                      
Retry loading it as a compressed image.                                        
Code Address: 0xFFFFFFFF, Entry Address: 0xffffffff                            
Failed on decompression.  Corrupted image?                     

this even with "common" from openwrt's compilator/buidler .binaries, or with "transformed by flashimage" process :


    #!/bin/sh
2 parameters : first = input second = output
cat /dev/zero | tr '\000' '\377' | dd bs=64k of=$2 count=128 seek=0
dd bs=64k of=$2 if=$1 seek=1
dd if=/dev/zero bs=64k of=$2 count=1 seek=127

how would it possible to fix it via tftp?
i thank you vm!
here are the bootlogs :