Playing video games is a surprisingly underrated way of developing vocabulary and reading skills in new languages.
I'm not even talking about educational video games or "gamified" rote-learning language apps. I'm talking about regular video games that let you change the default language.
Video games allow you to immerse yourself in the language. You're forced to actively improve your language skills if you want to progress through the game. You'll need to learn a new word to understand what specific object a game character just asked you to find. For some words, maybe you don't bother to look them up, but you constantly read them in certain contexts and, that way, realize what they mean. In the game, your character's tool inventory shows you pictures of objects with their corresponding labels, so they basically act as vocab flashcards. Finally, regardless of how you learn any new words, you're sometimes even able to associate these words with the specific part of the game where you encountered them: a village, a beach, a castle, a dream—the game world acts as a memory palace, helping you remember the vocabulary more easily.
Of course, the game needs to be at the right level of language learning difficulty. I wouldn't recommend this for someone who doesn't know anything about the language at hand. Yet, after learning the basic grammar, vocabulary, and phonetics of the language, it seems like a great technique to expand your knowledge.
For beginners, it seems best to play a game where text isn't too frequent and the grammatical structures are simple. For more advanced language learners, text-heavy games with complex grammatical structures, more advanced vocabulary, and even some wordplay provide more learning opportunities.
Last year I finished playing Breath of the Wild in Italian and now I'm playing some less text-heavy games in French. I wonder how much playing Ocarina of Time and other games helped me learn English in my youth.