I wrote a book on habit formation in apps. https://usetemper.com/digital-behavioral-design/
I run a sub-reddit that get's at least 1 post a month from someone launching a new habit tracking app. https://www.reddit.com/r/Habits/
My last company made SaaS to help app publishers understand and strengthen the habits in their app. https://www.crunchbase.com/organization/dopaminelabs
I'd add one item to your list: No one wants a habit tracking app. A lot of people could benefit from one, but when people have a problem in their life (sleep, diet, productivity) they almost never conceptualize it as a habits problem. They look for tools to "improve sleep," or "be more productive" but not a habit tracker.
My new company (https://usetemper.com/) is all about habits and behavior change, but that's mentioned almost no where on the website because that's not how our customers think about their problem.