I am trying to make a flutter camera app. For this, I found a package named camera https://pub.dartlang.org/packages/camera which has been written by the flutter team itsel
The code for that package:
https://github.com/flutter/plugins/blob/master/packages/camera/android/src/main/java/io/flutter/plugins/camera/CameraPlugin.java
uses Android Camera2 API
and from this thread https://github.com/flutter/flutter/issues/9310 you are free to fork and create a version which supports the older Camera API available in KitKat