Is it possible to make money using your Linux knowledge if you're not a developer? I know I can become a professional devops or sysadmin if I take some courses and master advanced networking. But is there something I can do now as an average, moderately experienced linux user?
It's the opposite, I don't make any assumptions on OP's knowledge but my understanding of your comment is that you are assuming that he is just the average Joe that likes Linux but might not be able to teach on the subject.
I just told him that teaching is an avenue he could look into and he agreed. Nothing more here.