Phone/tablet apps tend to be written in IDEs and Languages specific to their environment, if just for the sake of maintaining compatible "look and feel" with the environment. Often these seem quite-a-lot like the "Arduino Language" - they look an awful look like some "normal" development language, but have tweaks to make them easier to use for "apps."
For instance, I found:
As an iOS developer, you can program in native languages such as Swift or Objective-C or build cross-platform native applications using React Native (JavaScript) or Xamarin (C# & F#).
The primary and officially recommended language for Android development by Google is Kotlin. While Java was historically the official language and remains widely used, Kotlin has gained prominence due to its modern features, conciseness, and improved safety features like null-safety.
Javascript and HTML5 are languages that have a better chance of working on multiple platforms (typically through a web browser.)