For language you might be interested in the Clozemaster[0] approach. Basically, you are shown a sentence, both in English and the language you want to learn, and one of the words in either one is a cloze deletion, e.g.:

    English: there are thirty days in April.

    French: il y a trente ___ en avril

And you have to complete the cloze with "jours".

The sentences are compiled automatically from Tatoeba[1], the cloze deletion is done on the least-common word[2]. This combines vocabulary with grammar.

I didn't like the Clozemaster UI so I wrote a script to make the clozes myself: https://borretti.me/article/building-diy-clozemaster

But automatic approaches are not great. Later I asked GPT-4 to make these flashcards for me, that gave me much better/more meaningful results.

[0]: https://www.clozemaster.com/

[1]: https://tatoeba.org/en/

[2]: https://www.clozemaster.com/faq#how-are-the-blanks-in-the-se...