You can get into the iPhone or Android and copy the SQLite database to your computer. The images can be tricky - some form of reference to the image in your ph

You can get into the iPhone or Android and copy the SQLite database to your computer. The images can be tricky - some form of reference to the image in your phone, hard to put together; otherwise the messages in all the chats are in the database, navigable by a SQLite client. Speaking from personal experience porting messages from iPhone to Android.