Yes, I definitely profit from basic skills that I acquired in studying mechanical engineering, as you mentioned. However, when applying for jobs I didn’t have the impression that my prospective employers valued that too much, at least as far as my CV is concerned.
Not sure what you mean by “boredom”? I don’t have a clear “definition of done” or a deadline for my sabbatical, that’s also why I try to diversify the topics I’m looking at rather than going through them one after the other. I’ll definitely need/will start working again in a couple of months, but my hope is that working freelance and continuing self-studying is not mutually exclusive. But I’ll need to see next year how this works out then in practice.