Top 6 Mobile App Development Technologies
1. Python
2. Java
3. Flutter
4. React Native
5. Swift
6. Kotlin

There are also so many no-code app development platform is available now
(https://techwink.net/blog/7-best-no-code-app-builder/)

If you want still to develop an app here some hard code app development languages you can consider.

Flutter
Developed by Google, Flutter is an open-source mobile app development SDK (software development kit) that facilitates developers to create cross-platform applications. Yes, you read that right. By using Flutter, you can make an application that runs smoothly on both the Android and iOS platforms. Technology is highly demanded because people these days are preferring cross-platform applications over native applications that run only on a single platform.
The technology uses Dart as the programming language to build native interfaces. It also relieves developers to write the entire code from scratch to develop a single app for two platforms. Google Ads, Xianyu by Alibaba, and Reflectly are the three popular mobile apps developed using Flutter.

React Native
Developed by Facebook, React Native is an open-source framework used to develop cross-platform applications for iOS, Android, Web, and UWP. The apps developed using React Native have native-like capabilities and can run on multiple platforms.
Developers use ReactJS and JavaScript to create applications that witness skyrocketing success on different platforms. Myntra, UberEats, Facebook, and Airbnb are some of the apps that have been developed using this framework.