I keep EVERYTHING out of my dog’s reach. Every single thing I think he would chew up or destroy is hung up, on a high shelf, on the kitchen counters, etc. Dogs chew. That’s a fact. What is the harness made of? He could find that texture very appealing, so get a toy that mimics that.
98% of behaviors can be corrected with training. General chewing is not really one of them, but you can at least curb it with the right tools. When my dog started chewing on a specific pillow, it was taken away, but I made a note of the texture. It was kind of like a rope meets kevlar, so we got him a firehose toy and he loved it. When he started chewing on the baseboards, we got him harder toys, “branch” toys that mimicked wood, and he would go for those instead. He was also a puppy during this time, and now as an almost-adult, he doesn’t go for household things, but his own toys.
There are some things that dogs just DO. It is your responsibility to curb it and make something else more appealing and fun. And keep things out of reach. Buy a hook and hang crap on the wall next to the door, or get a shelf or something. I don’t understand why these items are left out for him to get into. That’s just silly. You’re a dog owner and things have to be put away, easy access or not. So buying these items over and over again so you have easy access makes more sense than simply keeping them out of reach and you have to walk an additional 30 steps and open and door to get something? How silly.