A small handful of the fonts support Cyrillic, such as "Squirk" and "Ninteteen Ninety Three", we don't add it to every font because there are only two of us and neither of us speak a language which uses Cyrillic characters - so it's a lot more work to make sure it's readable to native speakers & we don't always have the resources to do it. We're always looking to improve the selection of languages we support though so we'll take your feedback on board!