As I recall, the 1st version of Lato (which is available in google fonts) there is no Cyrillic. Cyrillic is only available with version 2.0 which is not represented in google fonts at the moment. About it writes the author of the font.
Dixie_Quigley answered on July 2nd 19 at 18:07
The same hat was with Raleway. First there was the Cyrillic alphabet, then has gone, and recently reappeared. That's just the italics for her as there was no and no. Had to go to the font author to get the latest version that has everything and which you can use. Google does not like the Cyrillic( And other services too. Have noticed that if in service, you can choose the font (at least the site Builder), then the clipped font Cyrillic, although it needs to be.
Kailey.Moore63 answered on July 2nd 19 at 18:09
Something I do not remember to have Lato Cyrillic seen...
checked Open Sans and Roboto - on the spot.