@marco_meier Those drives can use a 24v signal, however they will also accept 5v Step/Dir signals on the proper pins, so you can simply run 6XD 5v to CN1 pins 3 and 5, and Step- and Dir- to CN1 pins 4 and 6, respectively.
All you really need to concern yourself with voltage-wise is the 24v enable signal, which the Duet team has confirmed the 6XD CANNOT sink on the EN- pin. The enable circuit on my breakout board would do what you need, and you could easily coble something like that together without making the whole board. Really, any simple relay/electronic-switch style setup that allows you to trigger a 24v connection with the 5v-tolerant EN- pin from the 6XD will accomplish what you need.