They are apparently designing new courses with those levels in mind, and have adjusted old courses to fit.
We’ll be adding CEFR B1-level content to our Spanish, French, and English courses (about 2,000 more words in each!), up to A2-level content in other courses (like German, Italian, Chinese, and Japanese), and more overall practice with the basic four skills: listening, reading, speaking, and writing.
https://blog.duolingo.com/how-are-duoli ... -evolving/
So I think most of their courses target A2, and have ~5 levels/checkpoints/castles/stages, while some have more. e.g. Their German course currently has 6 levels/castles, while their French course has 10.