I've used Flashcards Deluxe for years and been very happy (no affiliation): https://orangeorapple.com/flashcards/ https://orangeorapple.com/flashcards/ Easy t

I've used Flashcards Deluxe for years and been very happy (no affiliation): https://orangeorapple.com/flashcards/ https://orangeorapple.com/flashcards/ Easy to import and export my cards, plenty of options for tweaking the algorithms for my use.