The short story is: software development. Sure, there are more quantitative jobs like data science and ML and other mysterious math/scientist jobs that are quite hard to find and secure, but software development of any kind is the quickest way to a job. You'll need to convince people you're not a pie in the sky thinker, and so I'd recommend building up some side projects. Functional programming languages will probably suit you better, and those jobs can sometimes be more technical. Also, universities and research institutions, at least in the U.S., are hiring more and more software developers.
Regarding trading and blockchain, having some principles is fine, but you also need to eat. There's nothing wrong with taking a job for a couple of years to get your feet into industry and then moving on from there.