Differential steering on fmuk66

I try to install firmware for the fmuk66. I can flash version 15.4 on fmuk66 board but as stated in the docs i can t build rover firmware for the fmuk66.
I tried afding the Config modules for mecanum / differential/ ackermann steering to the default firmware version bedoel build with no succes.

Is there someone who was able to install firmware on fmuk66 for Differential steering rover ?

Thx