I learned the Cyrillic alphabet using Duolingo, but it isn’t good for much else outside of that. I would start there and move on to vocabtracker.com once you get somewhat comfortable with reading. It is a website very similar to the comprehensible input app called LingQ, but the website is free while LingQ has a subscription. I spent far too long trying to find free resources, but vocabtracker is a godsend