Click on "Assemble GPlay Debug version" (or "Assemble FDroid Debug version" if you don't have Google Play Services), then click on "Artifacts" and then choose your apk from there.
How is that a solution to the problem? Of course there's other ways to install software, just like you could build your own iOS app and sideload it with a certificate. If an app is gone from the store it's basically dead.
If I were to test the implementation of an app in my enterprise, then it would benefit me to cut down on the unnecessary dependencies. Being dependent on the Google Play Store has shown to be a liability in the past because there were moments where it became a single point of failure (as demonstrated in this thread)
