Fluent Forever is an alternative to Duolingo which is based on flashcards which you customize from app-provided vocabulary and sentences, and are presented to y

Fluent Forever is an alternative to Duolingo which is based on flashcards which you customize from app-provided vocabulary and sentences, and are presented to you in spaced-repetition intervals. (The founder based the method off of his own experience learning languages with Anki.) The gamification is less than Duolingo. When I complete a review it praises me for my keeping up my streak, and they also added achievements. However there aren't gems, premium upsell ads (it's a paid app), etc.