Reading aloud stops a few minutes after starting (or shortly after switching off the screen). How do I fix this?

That might be related to energy-saving settings. On many modern Android devices, the system tries to stop background processes to save the battery.

The solution depends on your device model. Some manufacturers allow to include an application to the list of “exceptions” from the power optimisation mechanism. If your device has such an option, you need to include two apps: FBReader Premium and the text-to-speech engine.