Hi!
The Facebook-SDK.aar is in the thirdParty folder of the plugin or how ever you include it in your project. These .aar file can be opened like a normal archive file (e.g. with winrar). In this file (I can only speak for the FacebookSDK) you’ll find a res and some drawables folders. Inside of these drawables folders look for images with the .9.png ending and rename it to .png