Another possibility is tinea felis. It can be seen that the secretion in the ear canal is normal, without peculiar smell, and the prominent small lump is dead.
In that case, I suggest buying urea cream to apply. People's pharmacies sell them. Very cheap and natural, not afraid of cats eating or allergies ~ ~ hormone anti-inflammatory cream is not recommended. If the area of tinea is small, it doesn't matter if you don't apply medicine. The cat will be fine by itself. Pay attention to the hygiene of the cat's nest and the place where the cat often stays, and often disinfect and clean the nest pad in the sun.