I've had a lot of success with games like mastermind, stratego, uno, labyrinth and figure there's a lot of other ones out there but its overwhelming! Video games are coming up soon - but trying to build a base of content beforehand!
They'd probably really enjoy Wordle (and all the variations, like the math-oriented Nerdle.)
I've always wondered if two people could play a kind of "Hangman", but with five-letter Wordle words. (Kind of like the paper-and-pencil version of Mastermind, but with letters...)
The objective is that you both say a random word. Then both those words together make you think of a different word, and you keep going until you finally both come up with the same word. It goes on really wild tangents, so how you start has nothing to do with how it ends.
Uno works well for us.
Random board games from the public library. Some work, some not, but we don't spend money to figure it out.
8 year-old can already play games like Pokémon Trading Card Game. While that's absolutely a money sink, it encourages them to read and do simple math.