I wouldn't recommend feeding a dog, cat food!
It's generally way too high in protein and fat.
Long term, I can see it possibly posing a lot of problems like gastrointestinal upset, obesity, pancreatitis, nutrient/vitamin deficiencies etc... ASPCA | Feeding Dogs Cat Food
Also if you're switching between different brands, that might be upsetting his stomach as well. Did you do the switch gradually, over a span of a week or two, each time?
Was the cat food he inhaled, wet or dry?
When was the last time you checked out his mouth/teeth?
Has he had his teeth cleaned, recently?
Does he have bad breath, inflamed gums? If so, maybe a trip to the vet would be a good idea. Plus a thorough check-up could rule out other possible medical reasons as well.
You could always add a little boiled chicken or low sodium chicken broth to his kibble to make it more appealing and see if it entices him to eat. What kind of dry food are you feeding? Have you done any hand feeding or used his kibble as a reward for training? I have one dog who wont eat unless I make a game of it or hide her kibble in towels or blankets or make her chase it across the floor. Annoying, yes but it is literally the ONLY way to make sure she gets what she needs....she has me well trained
I wish you luck, getting to the bottom of it.
Welcome to the Forum btw!
It's great to have you here