Duolingo is a mostly-free app for learning languages. It is as easy as downloading the app to start a learning journey. From Wikipedia, "as of November 2019 the language-learning website and app offer 94 different language courses in 23 languages. The app has over 300 million registered users across the world."
Mango Languages, which CeLT used to sponsor for IU community in the past, is a free-to-library-membership or paid-for-single-use language learning service. Though its contract with CeLT expired, it remains to have partnership with Monroe County Library as well as Brown County Library. It offers 71 language courses, including rare-to-find courses of Dzongka(Bhutanese), Javanese, Shanghainese(an extinguishing dialect of the most influent area of China) and several more languages that are not listed in CeLT language list and its English courses are offered in 17 languages, according to Wikipedia.
The new logo of Mango Languages