As far as I'm aware, apps not natively signed by the dev are instead signed by nostr:nprofile1qqs83nn04fezvsu89p8xg7axjwye2u67errat3dx2um725fs7qnrqlgzqtdq0 and you have to wait for him to sign the latest apk. If you use Obtainium, you're pulling the updated apk straight from GitHub.