Language Learning Apps Harvest Data

https://sh.itjust.works/post/5722866

Language Learning Apps Harvest Data - sh.itjust.works

I should have known if the apps free, you’re the product. Duolingo appears to harvest the most data compared to other language learning apps. Source: Surfshark Research [https://surfshark.com/research/chart/data-hungry-language-apps]

Does anybody know some open source language learning alternatives? Preferably Linux or Android
Anki
Although useful it’s hardly on par with Duolingo.
Your own learning resources + Anki. However, this requires significantly larger amount of work compared to said learning apps, which has establisged learning course in bits and pieces. You need to digest your own textbook and such into small cards, it’s essentially building course by yourself. Fluent Forever from Gabriel Wymer gives some idea on how to utilize Anki, though the author moved built his own closed source app.
If there is no alternative at the moment, this is a good opportunity to build one.
I’m lacking the skills unfortunately.