Starting this past Saturday, Frontier began revenue flights with its new Embraer E-175s. I believe it will show up on FA as Republic, since Republic is the actual operator for these birds. I wouldn’t be surprised to see F9 put these on one of their 2 daily flights in/out of KCAK. They started with the A319, then downgraded to A318s.
BTW: In case you’re wondering, the first pic I saw of one had a sheep on the tail.