I asked at each restaurant we went to for breakfast.
At Akershsus, I received turkey sausage (by request)
At Early Morning Magic breakfast at MK, I received chicken sausage (in buffet line). They had chicken sausages and pork sausages.
At 'Ohana, I requested and received turkey bacon (I learned about this on the Dis

)
At Garden Grill I requested and received chicken sausage.
I didn't ask at Crystal Palace or Tusker House breakfasts, because they are buffets and there was lots to choose from, but I'm sure you could have gotten turkey or chicken items there too. I find Disney so accommodating.