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
If there is no alternative at the moment, this is a good opportunity to build one.
I’m lacking the skills unfortunately.