Several YT'ers suggested ordering samples from different dog food companies and that is what we did when Sugar Bear would not eat the Wellness Core Small Breed Kibble that we bought for her.
I only sent two requests, but we got (kibble) samples from Chicken Soup for the Dog Lover's Soul (2 small packs) and from Taste of the Wild (
8 small packs !!). If we ever have to change her food, I will definitely send off for samples before buying whole bags of a new food!
Someone suggested doing a taste test to see what your dog will eat, and that worked for us. I taped the names of each food to the bottom of 6 small saucers, placed 10 pieces of each kibble on each and laid them in a row for Sugar to sample at dinner time. I called her into the room and watched what she did. She turned up her nose at Wellness, sniffed and ignored Chicken Soup, ate most of the TOTW Bison, picked up a TOTW Lamb and dropped it on the floor, ate a few TOTW Roasted Fowl, polished off the TOTW Salmon, then ate the remaing Bison & Fowl.
Now we have three kibbles that she likes, and we feed her a different flavor for each meal, followed by a spoonful of Wellness (beef, chicken or lamb) or TOTW (fowl) canned food. I love the sample & taste test ideas I learned here!

Guess I should request treat samples now since we haven't been able to find healthy dog treats that she likes.