I would like to learn a couple of languages (polish and Japanese - I already learned Spanish to a decent degree) but it seems like every solution is closed source.
I would use books but listening (and speaking) are very important and books won’t help with those.
What would you guys recommend?
I hear this opinion a lot, and I’d just like to add it manages to help with some exposure and repetition at the very least. I’m sure you’re more knowledgeable than myself with learning languages, but I’ve been using Duolingo to learn Japanese for a little while now and have managed to pick out basic hiragana and katakana here and piece together small words.
I don’t have any delusions that I’ll be fluent if I finish this course, but if it can help me learn the characters it’s worth the time to me.