For iOS apps, there are a couple of hints you can look for: How old is the version of iOS supported by the app? If it is something ancient like iOS 9, very st

For iOS apps, there are a couple of hints you can look for: How old is the version of iOS supported by the app? If it is something ancient like iOS 9, very strong hint the app is written in ObjC. Take a look at their github page. Do they publish any popular iOS libraries? Are they written in ObjC? Objective-C is also indirectly popular, by virtue of React Native being written entirely in ObjC.