Step zero

Finding language/market fit should be "step zero" for startups as it can save you a lot of time and wasted cycles.

Founders should generally consider the search for language/market fit as part of the customer discovery process. (There are examples where this is less critical in certain contexts such as biotech startups or founders who are building products to scratch their own itch.)

However, if you've started with building and aren't finding a product/market fit yet, take a step back to find a language/market fit.