Comment by brightball

Try to learn a different writing system, alphabet or not. Arabic, Cyrillic, Hangul, whatever. It has finite number of cards and you don't need large context to understand them.

Language learning is the classic use case, but I also use it from everything from historical facts to encyclopedia entries on a subject I’m trying to master.

Probably the simplest use case to get started is improving your English vocabulary. (Assuming English is your first language.) I try to add a card for any word I come across that I don’t know the meaning of, and it works very well.

A quick and easy one is learning the NATO phonetic alphabet. You can find premade decks for it.

Leetcode patterns, and common problem types to apply those patterns to.