Jigsaw puzzles, the bigger the better. It keeps you constantly mentally engaged and the act of reaching for pieces and looking around is good physical activity too.
I get back ache if I do a jigsaw session for the first time in a while.
It really tires me out before bed and can prevent that rumination before falling asleep.
Finally it’s really cheap, there are limitless puzzles in charity shops and even some libraries lend them.