Ask HN: How do you research niche technology businesses?

I enjoy building things and have typically just built something to see if anyone wants it, because it was fun to build it. But I'd like to take a little more directed approach in the future. The problem I'm running into is I can find a lot of info on how to research, plan, and execute a VC scale business, but not much on finding a niche or lifestyle tech business. Some of the startup school advice still applies, but honestly not most of it. And I have found through experience I don't really enjoy the "get a million, scale as fast as possible or die trying" approach. Possibly because all mine have died trying, but still..

Making cheaper and less featureful versions of successful VC funded projects seems like a possibility, for example, but also kind of vague. Is there anyone writing good quality guidance on this, that isn't scammy? Or does anyone have anything to share?

My goal isn't to get rich, but to generate some passive income while building interesting things while I'm in semi-retirement.

If there isn't good guidance out there, what would you say are the most important attributes that make a good business of this kind?