I recently acquired my first dog from somebody who was moving away, but could not take the dog with them. The dog is a 3-year-old Labrador mix. We don't know what the other breed is, but I suspect a pointer.
The dog is amazingly well-behaved. He can "sit" and "shake", he doesn't enter any room unless given permission, he is able to spend a day or so alone, I am able to walk him without a leash, and he will return to me every time I call his name. He is also really kind with small children and friendly in general. When I take him on walks, he really enjoys jogging with me, jumping up on walls, and marking things. He will sometimes also jump up onto me in a playful manner, but very rarely. Another interesting thing I noted is that sometimes he will not eat his food unless either I or my wife stand next to him while eating.
However, I have been unable to get him to play fetch, or tug of war, or much of anything. I tried to buy him a Kong, but he ignores it, or is happy to get one treat out of it and then stop. I got him a chew toy and a rope, but they have been untouched for a week. I'm trying to figure out what sort of activities I can do with him inside the house to keep him entertained. Right now, I have to pet him a lot, or he just sits on his bed. I'm mostly concerned that he will get bored when we are out of the house and get upset, or start to become destructive, or I will have to tie him up in the yard.
I asked his previous owner what he did, and the previous owner told him he just let the dog hang out in the yard, but their yard was much larger than ours and the dog would sometimes run off and then return an hour or so later.
What can I do to get my dog to entertain himself?
Edit: Follow Up
It turns out that my dog does not need to entertain himself. He stays at home and does not ruin anything even when we are out for over 8 hours. (Neighbors come to see he is fed and take him on a walk) He prefers to "play" (going on walks/jogs, being pet, sitting in the same room doing nothing) with people, and not toys, but when alone, he does not appear to have a need to interact with any objects either.