Hi JD! Great question. If you don’t want to use Italian sausage, you have two easy options:
Substitute the sausage with the same amount of ground beef (keep the total meat the same).
Or, for a lighter version, you can replace the beef and sausage altogether with ground chicken—I’ve done this, and it’s really good and a lighter version.
Since the sausage adds a lot of flavor, I recommend adding a little extra seasoning either way: Italian seasoning, garlic, a pinch of red pepper flakes, plus a bit more salt and pepper to taste. Hope you love it—let me know how it turns out!