Well, since bug report section is off-limits to me as well, I'd like to secod the matter with TTS engine.
Apparently, it is impossible to override Google TTS engine with another one in accessibility settings. Upon calling for TTS engine, readers fall back to Google TTS. Tried multiple readers, multiple TTS engines.
The device I have is Pro 7 (Flyme 6.1.3.2g).

Edited by User5207442276 at 2018-05-12 20:02

So I have tried different stuff and found out that:
- freezing google TTS apk doesn't make things work.
- freezing google TTS apk and installing it under a different package name doesn't work. (Does it mean that only stock version of google tts is called by OS, and when it is unavailable nothing else is considered?)
- installing other TTS engines with higher intent-filter priority values doesn't help it either.
- installing readers with built-in TTS engines works, but this is not an option for me personally.

I am listening to books 5-!0 hours a day via TTS, and raspy and lifeless Google TTS makes my life miserable.