Arctic, but the TestFlight expires in 13 days, and the AppStore version was last updated 7 months ago. I'm not complaining, as it is free. However, it's the only app I've tried that has the swipe back option that Apollo had, and I find that really useful. If you want to return to the last post you viewed, from the feed screen you simply swipe from right to left.
Do any other apps have this feature now?