Hi @stevemann and welcome to Mayo Clinic Connect. I can only imagine the frustration of going to the dermatologist only to walk away without answers.

Here a bit on information on ankle rashes. "What does a rash around your ankles mean? An ankle rash can be a sign of a relatively minor condition, such as irritant contact dermatitis caused by exposure to poison ivy or poison oak. A rash on the ankles can also be caused by an allergic reaction to a variety of allergens (allergic contact dermatitis), such as grass." --- https://www.healthgrades.com/right-care/skin-hair-and-nails/ankle-rash

Have you talked to your neuropathy doctor about these rashes? Sometime rashes are a result of the nerve damage from the neuropathy. Also, what topical cream do they have you using?