I had one of the flight tracker apps, used it to identify planes passing my work lunch room's window, and paid $5 for it to get it ad free. Then it went to subscription and made it's free tier time limited instead of ad supported, so now I don't use it. I can't use an old version as it doesn't work on newer versions of Android

Edit to add: It's worth learning how to side load apps. While on a driving holiday in Sicily I was told that it was vital to have the ZTL app so I could know what areas were closed to cars (zero traffic limit), but it was only available on the Italian play store, so I had to download the APK and install it that way