Need ideas

I have a 1.6-year-old Golden Retriever named Remi. Horrible skin issues. I know that’s common for a golden retrievers. I’m not asking for advice on that. I have tried as much as I could. She has tried shots and pills. We now are on the hydrolyzed protein diet. The next step would be to go to dermatologist for dogs, which is very expensive and they said might not even figure out the problem. Obviously if she’s on the hydrolyzed protein diet, she can’t have bully sticks, antlers, dental chews, yak chews, collagen sticks, rawhide, etc… she normally gets one long lasting chew a night because she drives us crazy. It has been really difficult not being able to give her anything. They have hydrolyzed protein treats, but it’s literally just like her kibble. I’ve heard you could also get the soft food and freeze it and put it in a Kong, which I might try but I’m curious if there’s any other options? I know you could do ice cubes too, but that doesn’t really last long. Other than that, I’m trying to find some good mental stimulation toys. I know they make easy ones and hard ones. I’m looking for a difficult level but something that she can figure out. I also know they have those little grass pads where you have to find the kibble, but I’m not sure that would stimulate her for much time. Does anyone have any recommendations on a specific product (that she can have with her diet), or something I can do? Thanks.