For Mandarin Chinese, I found the Chinese-specific apps HelloChinese and ChineseSkill to be much better than Duolingo. Duolingo seems to follow a one-size-fits-all approach, and it suffers when faced with a language with tones, a complex character system, a romanization system commonly used for learning (pinyin), etc. Those other two apps have been called Duolingo clones, but they were designed with Chinese specifically in mind and it shows, they're leaps and bounds better.
I also have found The Chairman's Bao (news, curated and graded by HSK level, together with pinyin, vocabulary, grammar points and questions associated with each piece of news) and various Coursera courses helpful.
There is also plenty of crappy apps and resources around, and probably much better resources than the current ones will be made, but if one chooses well, it's amazing how easier it is to learn a language now than ten years ago. Getting to any nontrivial level of Mandarin Chinese was all but impossible without classes, now it's doable.
Much appreciated. I have been learning Mandarin on Duolingo. It was mostly just for fun, but at some point it starts getting a bit frustrating (lack of notes, topics, reading longer texts).
I also have found The Chairman's Bao (news, curated and graded by HSK level, together with pinyin, vocabulary, grammar points and questions associated with each piece of news) and various Coursera courses helpful.
There is also plenty of crappy apps and resources around, and probably much better resources than the current ones will be made, but if one chooses well, it's amazing how easier it is to learn a language now than ten years ago. Getting to any nontrivial level of Mandarin Chinese was all but impossible without classes, now it's doable.