I dug up my old 3DS in the past weeks, installed some custom firmware to play my backups of DS/3DS/GBA games. A bit of Zelda Minish Cap, some Metroid Fusion... But mostly I find myself playing various Pokemon ROM hacks lol.
I've been getting into "Pokemon Elite Redux", which is a difficulty/challenge game centered around each Pokemon having up to 4 abilities at the same time in battle. And there's tons of new abilities that make each pokemon uniquely useful. It's certainly challenging, even on the lowest difficulty. It's happened to me several times that I have to get together a whole new team to beat a single trainer.
But, there's zero grinding involved, and there's SO many quality-of-life changes that it's super easy to get a whole new team squared up in just a few minutes. That makes it really easy to jump in for a few minutes when I can, without feeling like I'm wasting my time