I’ve never been a runner (had knee problems that weren’t discovered and fixed till I was almost 40), started with a simple interval running app (Just Run), and was stunned by how quickly I went from barely being able to run for 1 or 2 minutes to doing a full 2k (though not fast).
A couple other apps:
Map Runner
Zombie Run (uses a story of zombies chasing you to setup the intervals, like listening to a podcast or a movie while running)