My Spotify plays heavy metal or Minion covers🥲

You have to actively and consistently break out of your regular patterns if you don't want the algorithm to force feed you a select few topics or push you down certain rabbit holes.

But what if he likes coding and compost? Is coding something else than digging through manure anyway?

Yes, it's also producing said manure.

Also, if he's satisfied with what the algo provides, no need to do anything.