Went through something similar with my dog when we adopted him. We'd pour the food for him and he'd just look at the bowl, then back at me, then back at the bowl, back at me... and just wouldn't eat it! It took him some time to get comfortable with eating around us.
You say your dog is recently adopted. Remember that he's just been through a big change and he doesn't really know you yet. This will improve as he settles in. Do you know his history? Maybe he had some negative experiences around eating.
What do you do after you place the food down for him? If you're just standing there, staring at him and worrying because he's not eating, he probably feels the tension. You could try putting the food down and leaving him alone with it for a while, giving him the chance to eat with some privacy and at his pace. Sounds like he is eating when you're not home so this seems like it could work. (This was the issue with my dog btw - after he formed some trust with us it went away.)
If he's maintaining his weight (and it's a healthy weight for him), he's eating enough food, even if you think it's a small amount.
It also doesn't have to do with him "disliking" the food - if you are feeding an AAFCO-certified food and it's not causing him digestive problems (gas, bloating, diarrhea etc.) then it's a good food for him to eat.
Good luck and try not to worry too much, I think this will resolve as he gets used to you and feels like he has some personal space. If it keeps up and he starts losing weight/becoming unhealthy then definitely see a vet.