Unsupported Modules Detected: Compilation is not supported for following modules: GettingStartedFirebase, app. Unfortunately you can't have non-Gradle Java modules and Android-Gradle modules in one project. code example
Example: capacitor-android. Unfortunately you can't have non-Gradle Java modules and Android-Gradle modules in one project
1- close the project
2- close Android Studio IDE
3- delete the .idea directory
4- delete all .iml files
5- open Android Studio IDE and import the project
Answer from here