We already know enough about chemistry and physics to rule out the possibility of building transistors inside the sun, or any other useful permanent structure inside a star. At the opposite end of the spectrum, we're already commercially exploiting temperatures on par with deep space and extremely low pressures. Yes, there's a lot we don't know about the properties of things or conditions that are hard to keep around in large quantities in the lab. But we're not going to discover complex life or be able to engineer complex and cost-effective machines in conditions where there's so much energy that molecular bonds can't stay intact or where there's so little energy that nothing gets done at better than a glacial pace. There's surely interesting stuff left to be discovered in those fields, but we won't magically stumble across a plasma-based computing substrate that is better than what we can already do on Earth.