What the f*ck CAN I feed my cat? Urinary problems, allergy with Iams, losing my mind

My cat used to eat Purina One weight loss food and Friskies. I heard all that was bad for her so I switched her to Iams. She was on the chicken flavored Iams weight loss and hairball recipe for dry, and Iams perfect portions chicken and tuna. She was never itchy until I introduced these two. Now she was itchy all the time. I took her to the vet and they said stop giving her chicken she might be allergic. Come to find out many other flavored cat foods still have chicken in them.

Now I think I've narrowed it down to the Iams dry food because as soon as I give it to her she itches. I've changed her wet food already to Tiki Cat seafood.

Now I'm learning it's bad for cats to have seafood as a main part of their diet. Fine, I add Tiki Cat beef pate and some pumpkin. But google says even a little seafood could cause them neurological issues. I don't think she likes beef very much.

But really, if your cat is allergic to chicken what is the best thing for them to eat? I'm tempted to just say fuck it and go back to friskies at this point because she wasn't itching while she was eating it! This allergy took weeks to show up and came out of nowhere. She also got a UTI. I'm so stumped on what to give her that's the absolute best for her diet.