Yes, I actually did!
One of the 3 N. Campestris tubers I have was not growing it was starting to "mushify" a bit so I decided to cook it!
It was covered in algae so I cut off all green parts to be safe and ended up with a small cube.
Then, I boiled some water and tossed it in. I let the cube boil for 5 minutes.
After that I cooled it down in some water.
Tasting results:
It tastes like an undercooked potato mixed with the white part of a melon, but mostly undercooked potato.