But in general it’s just understanding what makes people happy: dopamine. And then understanding how that specific person varies from average.

Like, it’s entirely possible they keep doing all things that would make most people happy, and they’re just wired differently so it’s not working.

This is where my answer would go to. I’d extend on what you said about dopamine though in two specific directions:

• Learn what drives you as an individual. Besides chemical inducements, what actions/accomplishments/behaviors give you a sense of satisfaction? For most there is some form of creative or active pursuit like artistic painting, dance, woodworking, moto racing, skydiving, sport, memorizing trivia, study of a field of science, organizing, home design, or any number of the endless activities that exist. Figure out what it is that you like doing, and do more of it.
• Cut back on the chemical inducements of dopamine. If you can get the 10x-100x the dopamine hit you need from just putting a chemical in your body, the tiny bit of natural dopamine you get from a non-chemical activity won’t even register with you. You’ll be desensitized to the natural dopamine you get from the things you like doing. The things you like doing that would normally give you dopamine won’t anymore that you’ll be able to detect. This means you stop doing the things you like. So the only way you can get any measurable amount of dopamine you detect is by the chemicals.