White-boarding challenges are--just as you said--a series of puzzles and nothing more. I also do lots of open source / make (significant) side projects, but I think it's important to be able to do these challenge problems and to be able to do them fast and to explain yourself well. I just can't respect another dev who can't reason through toy problems fast. The difference between a dev who can't toy program and one who can is the difference between a mechanic and an engineer in my opinion.
Anyway, something that has helped me get far in industry is writing detailed blog posts / post-mortems for my projects. They really help convey the fact that you know what you're doing and that you're passionate, and it's there that you can show that you have mastery of all these domain specific conecepts like `Joint Tables` and `Freshness` algorithms. You post those articles on LinkedIn and I guarantee recruiters will be all over you. Recruiters from real companies that you actually want to work for. At least that was the case for me.
Anyway, something that has helped me get far in industry is writing detailed blog posts / post-mortems for my projects. They really help convey the fact that you know what you're doing and that you're passionate, and it's there that you can show that you have mastery of all these domain specific conecepts like `Joint Tables` and `Freshness` algorithms. You post those articles on LinkedIn and I guarantee recruiters will be all over you. Recruiters from real companies that you actually want to work for. At least that was the case for me.