Russian spell cheking in spark 2.5.8

Is there a way to enable russian spell cheking in spark? Looks like it’s only cheking english, although the client GUI is translated in russian.

GUI translation is not related to a spellchecking. Btw, GUI translations are mostly done by a community members. As about the spellchecker, as far as i know, this plugin was bought from Wintertree company and it supports only English, unless someone will bought some other languages support (if they do have russian) and donate this to the Spark project. Well, personally, i think this plugin should be replaced with some open source project so it would be easily extensible. But so far this is not on a roadmap. So, sorry, no option for any other languages so far.