Into a large mixing bowl, add the torn pretzel bread. Set aside.
Into a large skillet over medium heat, add the butter. When the butter is melted, crumble in the sausage. Cook, stirring frequently, to brown.
When sausage is about halfway cooked, add the yellow onion. Continue cooking 2 minutes.
Into the skillet, add the mushrooms, garlic, sage, rosemary, and tarragon. Cook for another 5 minutes. Remove from heat.
Into the big bowl with the torn pretzel bread, pour in all of the mixture from the skillet.
Add unsweetened almond milk, provolone cheese, vegan egg substitute, sea salt, and ground black pepper. Toss together until evenly coated.
Into a greased 8x8-inch baking dish, pour entire mixture in an even layer. Cover and refrigerate for at least 1 hour and up to overnight.
Preheat oven to 350 degrees F.
Remove cover and bake 45 minutes, or until lightly browned. Let baked strata stand at least 10 minutes before slicing.
Serve warm.