The default TTS voices on Android (particularly older versions like Onyx uses) are not very good. Ivona is much better, but I don't think they offer Russian voice in Google Play (only on Fire tablets). I think there's a Russian voice from SVOX, so that might be worth a try.
Immersion reading with Kindle app is no solution as there are few titles in languages other than English. In fact it looks like there are about 2700 in German but none in any other language, which is odd. Probably something to do with regional copyright restrictions.
The Kindle app for Android does at least have Translate feature.
One could do worse than to get the $50 Fire tablet just for good Russian TTS. Though a Kindle might be better because it has a decent Russian-English dictionary (including indication of which vowel gets stressed)
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