There are so very many companies that exist in category c.) companies that make a profit from non-tech companies. Many of them are not public. Many of them are

There are so very many companies that exist in category c.) companies that make a profit from non-tech companies. Many of them are not public. Many of them are small. Many of them "only" pay SWEs as CPA-level salary. Many of them are working on "boring" problems. But there are plenty. If you're concerned about categories A and B, perhaps search for a position at companies in category C?