FLSun modifications time...
After all the struggle, design of a dual head adapter, printing, re design, printing, etc, finally all fits in place, I go cabling, all cables find their match on the Arduino.
But... it still works single head only, for the second nozzle heater receives zero input from Arduino, weird enough it also shows constant 100 Celsius (it is room temp in reality) and cannot understand why unless if they sold me a broken board hoping I never go dual.
And that is my guess for it. Broken board, defective, your call, probably reject from the production line sold as good as new hoping I do not go dual nozzle.