You can know the name of a bird in all the languages of the world, but when you're finished, you'll know absolutely nothing whatever about the bird... So let's look at the bird and see what it's doing -- that's what counts. I learned very early the difference between knowing the name of something and knowing something. Richard Feynman

--- in my case, it's fish & plant (started an aquarium ~ 3 years ago)

it reinvigorated my interests in chemistry (made my own PMDD fertilizer) ... soon i found myself browing wikipedias for KNO3, pH, nitrification, etc

it's about harmonius ecosystem ... focus on plant -> it improves water quality for fish which in turn feed the plant with waste

simplicity too (i abandon pump+filter+lighting+fert to soil+plant+sun+mulm) ... yes at the end i abandon my chemistry and my knowledge (nature always amazes me ... how little i know)

watching the fish and plant grow is like letting nature writing history for you ... unparallel to any books written by human

so i dunno about u ... maybe pick a hobby (preferrably ones that actionable, no theory -> see Feynman) and if u can make a business / startup out of it, even better