You did a mish-mash of different techniques.
If you smoke the turkey, don't stuff it. Unless you want smoked bread (not sure about using sourdough either...). And the low smoking temperature isn't really safe for cooking the stuffing (unless you take the stuffing out and bring it to safe temperature). The stuffing would probably also block the smoke from penetrating.
The brine should be heavily spiced and salted. If you don't spice the food, don't be surprised if it's bland.
Gravy. It should come from browned drippings from the roasted bird and roasted carrots, onions, and celery. I'm not sure where your gravy came from if you smoked the bird. The gravy is what ties the meal together. Don't skimp or take shortcuts since the gravy is used to complete the stuffing, mashed potatoes, and turkey. It's every bit as important to the meal as tomato sauce is to pizza or dressing is to salad (any of this "well if you need gravy to make it taste good then it must suck" is bullshit...sauces are 100% integral to some dishes). I fortify the gravy with homemade stock to make sure there is enough gravy for leftovers.
I typically smoke a breast with a few onions stuffed inside and spatchcock a whole turkey for quick and even roasting in the oven.
It's a simple and humble meal. Very humble. Any shortcuts will be obvious in the final product.
The reason even people like me who love turkey don't have it more often? They weigh 15-25 pounds. At regular non-Thanksgiving prices, one bird could be $50 or more. Plus properly prepared side dishes take hours of labor.
Smoke temp was higher than normal, around 150C. Stuffing actually turned out fine. Brine was Lane’s signature brine, followed packet instructions for quantity. Method I got from some obese YouTube chef with a southern accent so I know it was good.
As I said earlier in the thread, the meat was cooked well. It was juicy and tender and the skin was crispy from blasting it in the oven for 20 mins at the end. The issue was the turkey flavour itself (or lack thereof). I’m still yet to see one benefit of turkey over chicken apart from the size.
Whenever I smoke, be it chicken, brisket, ribs, or this time turkey, I leave a pan underneath to catch the juices. I use a charcoal barrel smoker so there are two levels - the turkey went on top and the pan below. I also rested the turkey for 30 mins before the final oven blast so that I could collect extra juices. Gravy was made from a butter and flour roux, juices, good quality chicken stock, and a tablespoon of chicken bone broth concentrate. Gravy was not the problem.
People want to criticise the cooking method, gravy, whatever, but they aren’t reading. These things weren’t the issue - the flavour of the meat itself was.