AAPT: error: attribute android:requestLegacyExternalStorage not found

(Material Files aurthor here)

You need to compile against SDK 29 and maybe use the most recent build tools for aapt to know this attribute, because it's introduced in Android 10.

Make these changes in android\app\build.gradle :

compileSdkVersion 29

targetSdkVersion 29

It will work.

Just delete line android:requestLegacyExternalStorage="true". You can use under Api 29.