Chewing can be a result of boredom or stress/anxiety, it is a natural behavior that many dogs enjoy throughout their lives. While enough physical exercise is great, dogs also need mental 'exercise' (stimulation) as well. A 'slow' walk at the dog's pace, where he is given the time to stop and sniff, investigate, follow his nose (within reason) can provide mental stimulation and tire him out , help him 'relax', both physical and mentally. Teaching tricks and new skills, clicker training for example: 101 things to do with a box - is fun and good 'mental' work out for them.
Management in the form of confinement, closing doors and baby gates limiting access to just a room or two, minimizes the risk of him finding inappropriate things to chew on. Providing a 'safe spot' ,whether it be access to an open crate, (if he has been properly crate trained) or a comfy dog bed that he has a positive association with, can be 'comforting' to them if they are feeling stressed with being alone.
Food puzzle toys, such as a Kong Wobbler, that he can knock about and the treats/kibble will fall out, can give him something to do. Or stuffing a Kong , or hollow bone, with his favorite foods/treats) even kibble soaked for 10 minutes then packed into the bone or Kong, or some peanut butter, banana (if he likes them), yogurt and frozen, and given when he is going to be alone, can entice him to work his brain and chew more appropriately, and give him an outlet for his energy, as well as help to relax him a bit.
Perhaps consider 'rotating' the toys, putting away all but a few, then
changing them out every day or two - to a dog a 'new' toy is 'fun' and more interesting/enticing to them.