I’m assuming there was no ID or contact info with it, since you probably wouldn’t be asking if there was.

Hypothetically, if you were to give it to the police, how would the police know that who the rightful owner is? If I walk into a police station right now and say I lost $200, do you think they would hand over $200 to me? No, I have no way of proving thats my money, and they wouldn’t believe me for a second.

Keep it. Lord knows everyone could probably use an extra few hundred bucks these days…

It doesnt look too hard to build from source if you want to go that route… You could just make a debug apk and install it with ADB.