Hiking. It costs nothing and you can create your own meaning from it. You can do the same trail over and over and know the place intimately, or you can make it a goal to do as many as possible and keep track of them all with souvenirs or art or whatever you want. The benchmark for success is what you define. And it's got a bonus of being good for your body.

I'd also suggest traditional music, but maybe keep it simple and cheap... ukulele, didgeridoo, or tin whistle. It's a low bar for entry and it's inherently social, all about jamming and being inclusive. Didgeridoo is more solitary, if that's what you prefer. These instruments have almost no ongoing costs and are great for learning the basics of music.

Instruments arr both humbling and also affirming. You can make noticeable progress and, again, define your own success. All my best friendships came through playing music. It's an endless source of joy for me. I generally tend toward depression but music keeps The Big Sad at bay