How to think of profitable startup ideas?

Don't let the fact that something already exists make you bail an idea. In our globalised and interconnected world it's very unlikely that something (similar) does not already exist. Instead, try thinking how your solution could be different. Not just from a feature perspective but also from a proposition perspective. Perhaps you could focus on a niche market, can offer a similar experience for less money, do a better job positioning the product, etc. At the end, how many of the products and services you use do not have competitors?

It's much much easier to build something you personally want or need. Have you run into any pain points that you wished there was a good solution for? If you can't think of anything, then the second-best option is to start talking to people in a particular niche that interests you (developers, amateur cooks, whatever) and start finding out what issues they run into.

I started looking at this website, https://www.trendhunter.com, for ideas and general trending themes. A lot of it is physical product-oriented, but there are also sections around Tech and apps. As an example, apps for wardrobe tracking, etc.

Pick something you care about and try to solve a real problem. I think it actually increases your chances of success because you're more motivated to improve the product.

Ex: I'm personally interested in edtech; I think there is not only tremendous financial opportunity in the market, but also the opportunity to measurably improve the way we learn. I felt personally underserved by the education system in the US (including higher ed), so in some ways it's the classic founder example of solving a personal problem, albeit on a larger scale.

Indie hackers itself is a great example. @csallen wanted a place to talk to people about building profitable software businesses, but it didn't exist yet. So he built it. It's not just a profitable business, but also a community that he deeply cares about. Think big!

This article by @csallen might be helpful - https://www.indiehackers.com/post/how-to-brainstorm-great-business-ideas-ab51c3d51c