Not only does every app need to have an export option, but new exports must create new, time-stamped files rather than overwriting an existing export!

A counter-example is "Battery Monitor Widget" by CCC71 or 3C71. That app creates a file in the main user directory, named "bmw_history.txt" (no relation to the car manufacturer).

When a new export is created, the existing bmw_history.txt is overwritten. This could lead to data loss if the user is unaware of this behaviour.

The developer thought of creating an export ability, but messed up at the file naming process.

Mandatory time-stamped user data exports for every app would not be so bad. This makes sure no developer would forget about it. GDPR gave us data portability for social media platforms. Let's do it for apps too. (Sorry, Samsung Internet, you can no longer lock in saved pages. Your users are sick of it.)