Yes, Russian is supported. The plugin itself is also translated into Russian.
The plugin works for all countries and languages. Squirrly SEO’s Live Assistant, Keyword Research, Focus Pages, Google Rankings Section — all of them work with over 140 languages and we’ve implemented Right-to-Left and we’ve adapted as much as our users from different regions have taught us.
You can use Squirrly SEO and do Keyword Research in multiple languages. The plugin supports over 100 research countries.