Not demodex -- pretty sure.  Could be fungal.

Remember -- ringworm is NOT a parasite.  It's not "worms".  It's fungus --

In humans ringworm looks like a series of red rings that overlay each other.  In dogs you don't see the 'ring' -- but you can see sort of a ring over ring pattern.

Think of the Olympic "rings" symbol except take the 'rings' out and leave the outer pattern -- looks like a ragged arc??  It doesn't look like connected 'rings' without the rings.  THAT is how ringworm tends to look on a dog.  The skin isn't discolored usually at all -- just "naked" where the hair has fallen off/broken off