Chronic ear issues :( - food change recommendations?

Our 10 (almost 11!) year old bulldog has recently begun having chronic ear issues 😭


We have returned to the vet on at least three occasions and last time we went were told next step is allergy specialist

After inquiring with specialist, their treatments and testing could be up to 2000+

We are hoping to try what we can before going this route (because we are struggling financially) but obviously love our guy very much and hate seeing him in such discomfort

His diet has been the same since he was little (holistic selects weight management formula) which is primarily a chicken and pea protein.

We tried to switch to a different protein source of the same brand (lamb and rabbit) but even after just a couple days it seems the itching is even worse.

Feeling super desperate and wondering if anyone has experience in this realm or could share what worked for them

My thought is to try something totally different like the Purina pro plan Vetrinary vegetarian ? And see how it reacts ?

We clean his ears regularily with solution straight from the vet and he only gets cucumber and broccoli as treats (he loves it) as well as a vegan glucosamine powder supplement on every meal

Any recommendations or tips would be so appreciated ♥