To me it's alpinism. Tthere is nothing else from the moment you touch the rock, snow or ice, to the moment you and your partner (if applicable) have arrived to the top (and sometimes after you have descended, because you also have to climb down most of the times). Your awereness must be 100% on what's in front of you and the immediate surrounding. Work issues, relationship issues, money problems, all has to disappear, and nothing else leaves me at peace like in those hours.
That said, I always wanted to get into woodworking because you still create something, but with your hands more than with your mind, and i love working with hands, but i don't have the space yet to get started.
I have that kind of relationship with several video games I play. It varies, of course; you can have anything from a quick intellectual puzzle like Sudoku, to difficult but self-paced games, to low/no pause games that strongly encourage a flow state (i.e., maybe you can pause, but it's not especially advantageous to do so).
Of the middle, FTL: Faster Than Light is my example; you are not only able, but strongly encouraged, to pause often: take time targeting your weapons, assigning crew stations, ship's systems, etc. I've played through it enough times not to read and cogitate on most of the messages/events, though it's not so engaging that nothing ever crosses my mind; or I may just get up and take a break, and then other thoughts drift back in.
The latter case, in the past I've played quite a lot of several FPSs. Like, I grew up on Quake 2 online multiplayer, and still play a fair bit of Classic Doom (the mods coming out these days are exquisite!). But most recently, I've been playing a lot of Rain World, a fascinating 2D survival platformer / simulated ecosystem / body horror / post-apocalyptic sci-fi game, which has more-or-less one-shot death, so, fail a jump and it's back to the start; or, just stand around too long and a giant lizard is likely to munch you (let alone if you're moving through an area strewn with them, among other hazards). It's not just that it's a challenging game, but indeed it
demands attention, and won't let you progress until you've shown your competency, at each leg of your journey. It seems like, of the range of people I've seen playing it online, a sizable number of them are very [self admitted] ADHD brains; I'm not sure if the game specifically helps with that condition, but if nothing else, the demand for engagement seems a surprisingly effective way to engage the hyperfocus flow state characteristic of ADHD. For my part, I find I'm rarely thinking about anything else while playing, unless some bit of lore happens to twinge me just right and I have to pause and give it a think.
There's probably a fair amount of merit to discussing games in this context, relating to lifestyle and relaxation, to mental health and so on. It's interesting that such things have generally been frowned upon to discuss in the past, perhaps seen as trivialities, or too off-topic; well, between societal expectations, and a growing sensitivity to our own mental health, perhaps there is room for them after all?

Tim