What is the Russian Language Pack application, how does it work?

According to the introduction of Menny Even Danan, Russian Language Pack is a Tools app on the Android platform. There is currently a 2.0.1 version released on Feb 22, 2017, you can see the details below.

This is a Cyrillic expansion pack for AnySoftKeyboard.
Install AnySoftKeyboard first, and then select the desired layout from AnySoftKeyboard's Settings->Keyboards menu.

This pack contains Cyrillic and phonetic Russian keyboard layouts, physical keyboard mapping and dictionary.

Search for AnySoftKeyboard on Google Play.

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https://play.google.com/store/apps/details?id=com.menny.android.anysoftkeyboard

* New Cyrillic keyboard