Does anyone know what t he is is?

My cat has had this for about 2 months, I’ve taken him to the vet multiple times. They aren’t sure what’s going on, they have given him antibiotics, steroid shot, and  had me change his food. Nothing has helped!! Last time was traumatic for him, they had to sedate him, and none of the suggestions helped. Trying to reach out and see if anyone else has seen this or had answers before I take him back again! TIA

*****2021-04-06T06:46:32Z

Did they biopsy it? Given the location, I would wonder if it could be eosinophilic granuloma? But if your general vet cannot diagnose it, I would request a referral to a veterinary dermatologist.