[knc1]

Your running a custom K3 kernel (and a custom initramfs) - AND - you have made other changes to your DXG to make it look like a K3.
That should be enough to break the 'model locked' update packages.

So repackage the *dxg_install.bin as a 'K3 modle locked' package to match your device changes.

AND
We do have the serial port connections for the DX(G) devices indexed.
Note: it is 3.3 volt, not 1.8 volt.