I understand your plight my man!

As another commenter said, forget LISP, forget open-source contributions, forget software dev itself.

Focus on problem-solving and DSA. I'm not sure what level of a software dev you are, but OS, Networking, DBMS, and System design might all be important as well.

Today's software interviewing is purely a game of problem-solving and DSA.

Grind Leetcode, look up InterviewBit, and refamiliarize yourself with DSA and problem-solving paradigms.

You're someone who enjoys complex probability concepts and tedious discrete math.

Problem solving will be a CAKE WALK for you. Just needs some focused practice.

Wish you luck my man!