lberrymage It's assumed that users will use system navigation (i.e. gesture or 3-button navigation) to navigate backward through the app, which is why there's no back button. We can reconsider this, but it is currently possible to navigate backward through the app.
I also vote to implement an in-app back button, for clearer navigation. If your repo has an issue open for this I'd be happy to comment there too. My experience, as a "digital native" and very tech savvy, is that lacking back buttons leads to confusion about where one currently is in relation to the rest of the app. I've used several apps that use your approach, like Neo Store and SystemUI Tuner, and in all of them I frequently exit the app accidentally because I thought the OS back gesture will take me to the previous screen in the app.