What is an appropriate job role for a BA level theoretical mathematician
whose primary interest is the deep math of computers? Chip designer maybe? What else? Get a job which allows you to get a masters or phd. You're competing in a space which is grade/level aware. Quant in fintech, learn a mathematical language like Julia for rigor. Or, a formal proof system like coq or Isabel, and Haskell. Before the edit, the question read: "Outside of academia,..." Jobs outside academia exist which encourage further education, or which are adjunct to academia. So, data science in government, or government funded industry, or in an industry like civil engineering where people have a CPD obligation. My employer in the NFP sector pays msc and phd fees, if not the full costs of study.