Who are the strongest non-professional GMs? As title above states, who are currently the strongest non-professional chess players? By this, I mean players who have a full-time job outside of chess. For example, I remember German GM Georg Meier mentioning in an interview in 2018 that he has a full-time job in a bank.
Up until recently, that title would have gone to Teimour Radjabov without question in my mind. Since April of 2015 until last month, he has only played 149 games. That is not many for a top-flight GM over four and a half years. That said, he just won the right to play in the Candidate's, so he may becoming more active again.

Quite a number of old GMs were musicians and engineers. GM Mark Taimanov was also famous as top concert pianist in the Soviet Union. Mikhail Botvinnik was famous for being an electrical engineer and computer scientist while also being the world champion at the same time. Dr. Ruben Fine was a Doctor of psychology. GM Helmut Pfleger of Germany is an MD.

GM Lars Bo Hansen is 2560, and is an Assistant Professor of Sport Management and Business Strategy at Florida Institute of Technology in Melbourne, Florida.

As stated by Ian Bush, Luke McShane is considered the strongest with an outside full-time job, but I am not sure I would give him the title "of strongest non-professional GM" based solely on that as he plays a fair amount, and has played 182 games in the same time frame as I listed for Radjabov. Based on that, and the 100-point difference, I still have to go with Radjabov.

Here is a cool list of chess players, who have doctorates.