As an indie hacker do you need product market fit?

You don't. 100% sure about it. In fact, you don't need it to be a multibillion dollar company.

Product market fit can be defined with clear. When you have a 20%+ retention rate after months (the number of months depends on your business model, but it always more than 6) or when 40% of your users would be very disappointed if you stopped proving the product/service, then you have product market fit.

Very very few companies have it and some of them are very successful. Slack doesn't have product market fit, just to name one, so you obviously don't need it. WeWork neither. Clearly the multibillion companies that don't have it are the exception, but I would argue that for the small business is the norm.

To make you somw examples.

There are tens of blogs that make 7-8 figures. How many people would care if they disappeared? How many of the people that signup for the email list unsubscribe? Maybe 5% in both cases to be optimistic?

How many restaurants and hotels did you try? In how many of them did you go back multiple times? What about ecommerce?

You probably get the logic here. To be a small business (6-7-even 8 figures) having a super small percentage of loyal customers (<5%) plus occasional buyers is more than enough to make good money.

Yes, you absolutely still want to build something that your customers love. One benefit of being a solo entrepreneur is that you can focus on a smaller market than a startup taking investment and by focusing on that particular subset of people, you can build a product that fits their needs better than a large company.

Of course you need some level of Product market fit. In a smaller market you will need more pmf than a larger market. Product market fit means that your product resonates with your customers to the point where - a) they stick around and b) they will tell others about it.
Generally Product market fit is spoken about in terms of being in a large market where they have a significant need that you are serving with your product. This results in scaling up quickly to becoming a large business.
As an indie hacker you don't need product market fit by this definition but you do need some product market fit. The result being you won't have to do as much work on the marketing / sales side. Focusing on your product will be enough to build / sustain momentum. This is key in that you don't really have the resources to do huge amounts of sales and as an indie hacker your skills are likely to be more aligned with building product.

From my point of view, yes you need it. Market/product fit in a small niche is market/fit too.

In mu understanding, market/fit is the degree to which a product satisfies the needs of the market. So even the smallest projects have to find fit between ux, feature set and value proposition and customer undeserved needs, if they want to have users.

Product market fit comes later...

First you need a market. If the market is huge, you don't need product market fit. People will buy your product because of sheer demand to (partly) solve their problem. If you want to gain real traction, you need PMF.

You always want product market fit, by definition. But for a smaller niche market, product market fit won't necessarily look like an explosive hockey stick growth curve.

Product market fit just means the market values your product. Your metrics don't need to be off the charts. If you have a few people who love it and pay for it, then that's all you really need.

I think your product-market fit is your metric for assessing whether you are building something your customers love. They are your market.

Zest does something called feature-user fit. Each feature of the design is tested to see how our users respond before it becomes a part of the whole. But whatever method you choose, you should be focused on discovering what your users will love and why.