It looks more like possible fur mites (“walking dandruff” than ear mites to me. Ear mites tend to be inside the ears, whereas fur mites occur mainly between the shoulder blades, around the base of the ears or the root of the tail – places where the rabbit can’t reach to clean themselves very well.
This could also be just dry flaky skin. It is very common on the backside of the ears esp if the bun is shedding. You can brush it off with a very soft baby brush. Some buns get dandruffy in other places as well when they shed.
Do you feel any unevenness when you feel the area with your fingertips? Mites typically cause yellowish-white (skin-colored) scabs that are easier to feel than to see. There is also always some hair loss with mites.
If this is fur mites, it will either go away (bun’s own immune defense sometimes fight them off), or get worse. Many buns don’t seem bothered by fur mites, others get very itchy. You will of course notice if your bun start scratching the ears a lot.
The best remedy for both fur mites and ear mites is Revolution (selamectin). A vet will need to prescribe that, unless you are in Australia. Some vets prefer to give ivermectin. Repeat treatment is sometimes necessary.
And now a public service message we always issue when anti-parasitics come up: Never use any compound containing fipronil on a rabbit. Fipronil is sold under many different names such as Frontline or Sentry. It is deadly toxic to rabbits. En of public service message