As a person perpetually stuck on the ‘total beginner’ phase, I really have no idea how one would start learning chess by beginning with openings. As I imagine it, one first learns to recognize good moves three levels forward, then four and five, until full positions start making sense quicker—and ‘endgames’ are a natural fit for this, since they involve just a few pieces and lead to an unambiguous checkmate. Puzzles, like in some phone apps, work pretty well this way. But openings are a complete opposite of this.

(I mean, I understand that in any case one proceeds to learn the overall game by memorizing hundreds of openings and training to recognize patterns at once, and then by dumping full-time evenings into cranking up the rating. Which is why I decided that I'm fine with the beginner status.)

Memorizing openings is dubious at best, unless you're already a very strong player. Most chess coaches will actively discourage studying the opening until the you've become sufficiently good at the more impactful aspects of the game. Things like, awareness of the board, not hanging pieces, king safety, tactical pattern recognition, calculating 2-3 moves in advance with precision, attacking, defending, basic endgames, time management, basic strategy, and instincts. Memorization, without understanding, is mostly useless in Chess.

Ehh endgames can quickly go from easy, a beginner could do it, to insane theory that IMs struggle with. Mating with a Queen? Easy. Mating with a rook? Sure. Bishop knight? That’s pretty rough. Knight knight vs pawn? Even Hikaru struggles with that one in blitz.

Give Lichess a go (mobile or website). It's got unlimited puzzles and has helped me tremendously and doesn't get monotonous

That is an interesting idea! I wonder if it would work for go too. There are fewer rules to learn, but the situations can get rather complicated too.

There's a term for go minigames in Chinese, but I don't recall it. You might enjoy this site: https://senseis.xmp.net/?ProblemsAndExercises

Tsumego is probably the term you are looking for. I have an app with lots of them on my phone.

I was talking specifically about using them to teach the rules, which is not something I've heard of so far.

thanks for the positive feedback! warms my heart <3 :)