ADHD here. Speedcubing. It’s a wonderful hobby for me. When I’m interested in it, I can learn some new things and time myself to see how I’m doing. When I’m not interested in it, I can solve it and it helps me to focus on watching TV. Even if I’m not solving it, it feels great just to twist in your hands.
Look up a good budget speedcube (not Rubik’s branded) and invest yourself as much or as little as you fancy.