Hey,
In the past I used Duolingo to study languages, but now I’m more privacy-conscious and looking for better options. And their recent data breach only solidified that intention.
I recently saw someone posted a comparison table for privacy policies of Duolingo and a number of competing products. Unfortunately I cannot find it now.
Can you give any suggestions? I’m not opposed to paid services, btw
Anki is a free and open source spaced-repetition flashcard program. You can find many premade decks for it for pretty much any language, and you can create your own cards from real-world content you read ("sentence mining"). You can also find free (or pirated) grammar guides and similar content online. These two resources will give you the foundation for making your input comprehensible, but the vast majority of the learning you'll do will come from simply reading and listening to native content while making as much of an effort to understand it as possible (such as by looking up words in the dictionary using a browser extension like yomichan)
https://apps.ankiweb.net/
See this really good guide for learning Japanese (some of the information applies to other languages too): https://learnjapanese.moe