Preheat the smoker, according to manufacturer's directions, to 225°F.
Remove the thin membrane from the bottom of the ribs. (see tip) Pat ribs dry with a paper towel.
In a small bowl, combine the yellow mustard and apple cider vinegar. Lightly brush the mixture all over the ribs.
In a medium bowl, combine the brown sugar, paprika, kosher salt, onion powder, garlic powder, black pepper and cumin. Generously pat the rib rub all over the ribs.
Arrange the ribs, meat side up, on the grill racks. Close the grill and smoke for 3 hours.
Meanwhile, turn up the edges of 2 large sheets of heavy duty foil and place side-by-side onto a large rimmed baking sheet. Pour ¼ cup (4 ounces) of the beer onto each foil section and sprinkle with 1 teaspoon of the lemon zest each. Discard or drink the remaining beer.
Using tongs, carefully transfer the ribs, meat side up, to the center of the foil. Wrap the ribs into flat foil packets. (see tips) Place the packets back on the smoker, seam side up, for 60 minutes.
Carefully open the foil packets a little at a time to let the steam escape. Using a fork, test the tenderness of the meat in between the ribs. (If more cooking time is needed, roughly close the foil and cook another 15 minutes.) Using tongs, remove the ribs from the foil packets and place back on the grill.
Brush the ribs with your choice of barbecue sauce. Cook, occasionally brushing with sauce, 45 to 60 minutes or until an instant read thermometer inserted into the rib meat registers at least 190°F and the ribs are tender. To test for tenderness, slightly turn 2 ribs opposite each other. If the meat gives easily, the ribs are done. If not, close the grill and continue cooking for 15 minutes or until tender.
Transfer the ribs back to the sheet pan, cover with foil, and let rest 15 minutes.
Cut ribs into individual ribs. Serve with additional sauce on the side.