Preheat the oven to 350 degrees F (175 degrees C).

For the dough: Combine flour and salt in a large bowl. Cut in shortening until mixture resembles coarse crumbs. Whisk water, egg, and vinegar together in a medium bowl. Stir into flour until mixture forms a ball.

Divide dough into 4 equal balls. Wrap in plastic and refrigerate for 4 hours or overnight. Roll out dough to fit two 9-inch pie pans. Place bottom crusts in 2 pie pans. Roll out and set aside top crusts.

For the filling: Combine apples, rhubarb, strawberries, blueberries, raspberries, and lemon juice in a large bowl. Combine sugar, flour, and tapioca in a medium bowl. Gently toss with fruit mixture.

Divide fruit mixture into 2 prepared pastry-lined pie pans. Cover with top crusts. Trim and crimp edges. Whisk together egg yolk and water in a small bowl. Brush tops of pies with egg wash. Cut a few slits in pie tops to allow steam to vent.

Bake in the preheated oven for 50 to 60 minutes, or until filling is bubbly in center and top is golden brown.