There's so many ways to fake your location data. There's one way that you can't really fake: Send them a secret code on a piece of paper in the US mail to their physical address. NextDoor used to do this at one point.
That seems a little excessive for an app like this. The only way I know of that users can fake their location is with a rooted device. I check for rooted devices in the app though so locations can't be spoofed.
Also, I hope you're not using Play Integrity (lol), because that means all the old phones you allow can be rooted, hide it from you and/or spoof positive chdck result........ because they're insecure like sieves..... Whilst you'd be banning modern and unrooted phones.