"Everyone talks about Product-Market Fit, but what actually matters is Product-Market-Channel Fit." — Tim Connors, venture capitalist
One day, I had a conversation with veteran venture capitalist Tim Connors in which he said that. Tim's point is that, ultimately, you'll need a great product, and you'll need to find the right channels through which to sell it. Many startups have died because they had the right product but the wrong distribution channels. Without the right distribution channels, your product will never succeed.
If you're selling home improvement tools, you'll probably need distribution through Home Depot or a similar big retailer. It's hard to sell books these days without being on Amazon. For mobile apps, garnering good reviews in the app stores is one of the most important ways your distribution will succeed.
Clothing brands have historically needed distribution through large retailers (or maybe a focus on selling through small boutiques). Today, clothing brands can choose to go direct-to-consumer instead, but a DTC distribution approach can be difficult and expensive.
So, as you're doing your Customer Development interviews, ask people where they currently buy products and services like yours. Understand the distribution channels available in your sector and the patterns of purchase behavior. You may even be able to test distribution channels at this early stage and see which ones appear to be most effective for your particular product.
Ultimately, you'll need a great product and effective distribution channels. So Tim is right—the sooner you start thinking about Product-Market-Channel Fit, the better.