I am looking for an Android instant messaging app that stores all chat messages in plain text format in my phone's internal storage or SD card. The availability of messages in plain text format is important because I want to be able to regularly and automatically backup/sync all my chat messages in a human-readable format. I do not want my data to be locked into the chat app, where I have to regularly jump through hoops to obtain plain text records of all my chat messages.
Additional criteria:
- Free and open source.
- Support end-to-end encryption.
- Able to send and receive images, in which case the images should also be directly accessible on file system.
Note: The plain text chat messages need not be importable into a different app. The important thing is that the chat messages are stored in plain text that can easily be synced and read using a text editor elsewhere.