[dottiesyrky]

Welcome to YT. :-))
I am sorry you are having these issues with food. It sounds like you have been through lots of choices for a picky eater! The first concern I would have is that he may have some underlying medical issue, even though his tummy seems ok. Did you tell the vet about this eating problem and have any tests?
Some, here have sprinkled a little Parmesan cheese or other tasty morsels on top of the food to entice their picky dogs. Some dogs are very fussy about the dish the food is in.....weird I know! Have you tried feeding him the kibble by hand at first until he gets the taste and eats the rest on his own? Do you have a regular schedule when you are at home and for feeding him? Does he get enough exercise to make him hungry? So many reasons out there for picky eating as you will see on YT!
I know I had a dog that would not eat unless a man was present!! My hubby, the painter....any male. LOL! Good luck, I feel for you having had dogs that were hard to feed. I am sure others here will give you their ideas too.