Duolingo was amazing for learning the Russian alphabet, something I struggled with from YouTube videos, etc. I can confidently read Russian nowadays (although I may not understand everything). I did get quite far in the lessons as well, but I don't have a high opinion of them. There were things I've learned from Duolingo that I said to native Russian speakers who were like... "we don't say that".

Note: The alphabet lessons are separate from the main content.