Recently Android Studio and in its last update 2020.3.1 has removed signingReport from Gradle sidebar but you can still get these details in Android studio in Terminal, just write the following command:
WindowsWindows:
keytool -list -v -keystore "%USERPROFILE%\.android\debug.keystore" -alias androiddebugkey -storepass android -keypass android Linux & MacOS:
Linux & MacOS:
keytool -list -v -keystore ~/.android/debug.keystore -alias androiddebugkey -storepass android -keypass android