Despite the presence of a translation into Russian, there is no way to set it as the default project language.
Actually, like dozens of other languages.
[Original text]
Не смотря на наличие перевода на русский язык, нет возможности установить его языком проекта по умолчанию.
Собственно как и десятков других языков.
Thank you for bringing this to our attention. We will look into expanding the allowed source languages to be in sync with allowed game languages. There was a previous limitation that blocked us from having more source languages but this is no longer the case.