Have you established WHY your dog is barking? Is it anxiety, overstimulation, boredom? Is it barrier rage, territorial? Is it barking AT people/animals, or just kind of yelling at nothing?
You need to figure out the why--the fix is entirely dependant on that.
If your dog is food motivated, you might consider mixing some peanut butter or sweet potato puree (not pie filling--sweet potato only) into some wet food or Gerber baby food (stage 1, meat only, is my default), then adding some kibble to it, stuffing it in a Kong, and freezing it. Freezing it makes it last longer. The kibble makes it a little more interesting, and the peanut butter/sweet potato/baby food addition makes the treat higher value than regular food.
You can also try treat puzzles as a boredom buster.
Odds are that these won't work for a dog experiencing barrier rage or that is reactive to people/other animals. It also prob won't work for a dog with severe sep anx unless it's REALLY foody.
Again, knowing WHAT is causing your dog to bark would help.
Also, is your dog getting exercise time, with you? Do you take him for walks/runs? After rereading your post, it sounds like you might have gotten a dog that doesn't fit your lifestyle--he's high energy, and you aren't, or are too busy to give him the exercise he needs. What kind of dog is it?
Folks tend to get critters that look good, and figure they can train them into the perfect dog for them. I'm not sure you came to be the owner of this pooch, obviously, and will help you if I can, with more details. But most working class dogs (hounds and terriers, for example) are smart and high energy--meaning that they need to flex their brains as well as expell energy. I'm surprised you didn't mention problems with tearing up the yard.... Wish I could hear the bark so I could tell more what's going on 🙄