So few people even say that the first step exists, or that it should come first, that alone is worth stating. Then go look for resources for how-to.
If a piece of writing does go further, it typically just advises the reader to do something like "Talk to people and find out," which is frustratingly circular. Talking to people is something most of us do every day without any profit, and "find out" just restates the problem.
It may be that this has been written about well somewhere, but I have never seen it. I figure it must be one of those things where you just have to figure it out for yourself, and for those who have figured it out, these vague platitudes look like actionable advice because they're able to mentally fill in the blanks.
Blog posts are by nature superficial, and more importantly, if you're reading blog posts by people in the tech world about marketing, you're probably picking the wrong teachers to learn from.
As a biz book nerd, who reads probably 30 biz books a year (for the last 12 years), I've never found one or even two resources that are end-to-end adequate. What I've learned, I've pieced together from hundreds of sources, including some meant for enterprise (and adapted for my needs), like _Pricing with Confidence_, and taking vague hand-wavy inspiration (_Purple Cow_) and looking for specific, real-world actions to make it concrete.
That's why I created my "30x500" course: to be a super-concise, super-specific crash course for nerd types (like me) who want to create their first product and want to do it with as little risk of failure as possible. I teach systems. I'm not gonna really pitch it here, cuz it's neither the time nor the place, but to say that I know what you're talking about -- and the stuff IS out there.
It either takes digging and work to piece it together into a strategy, or a willingness to shell out for something accelerated. My course is not the only one where you can learn how to do market research -- but you're going to be hard pressed to find it in one book, or two books, or 10 books, because the strategies and techniques to reduce risk are very valuable. And they take a LOT of work to create… I've spent hundreds of hours on building my course, doing research, tweaking the teaching methods & order, the metaphors, the workbooks, the homework, the supporting materials.
You'll rarely find that level of energy and diligence put into a business book, unless it's a byproduct of "workshopping" (like the GTD system was a workshop long before it was a book). Teaching workshops is vastly more profitable, and in a lot of ways more emotionally rewarding, than selling a book. So as blog posts are to books, books are to live classes & workshops. There's no equivalent reward for selling a $20 - $30 book with that kind of information in it... unless you can turn around and sell something more expensive, and leverage fame, like David Allen did.
That aside, there are courses & workshops where you can learn a lot more about step #1 -- other than mine! I've found these two to be excellent at the "figuring out what to sell" side of things: Presell Formula by Clay Collins, and Product Launch Formula by Jeff Walker.
Laugh if you must, yep it's internet marketer slumming, but they're really good at what they do. A person who wants to succeed won't sneer at any source of workable knowledge.