What is the simplest post-quantum asymmetric cryptographic algorithm for key exchange? This question has been burning in the back of my head for the past few days, and a quick Google search doesn't yield any usable results.
As the title suggests: What is the easiest-to-understand post-quantum asymmetric cryptographic algorithm that currently exists (as of 10 May 2021) for key exchange?
To establish common ground, assume that I understand everything from Khan Academy's Math Syllabus. On top of that, assume that I have gone through all of the undergraduate courses for MIT's Electrical Engineering &amp; Computer Science courses.
There is only one paper I know of which explains a post-quantum key exchange algorithm in such a way that a beginner could understand it, and that is for SIDH (Supersingular Isogeny Diffie-Hellman key exchange). The paper is called Supersingular isogeny key exchange for beginners.

Abstract. This is an informal tutorial on the supersingular isogeny Diffie-Hellman protocol aimed at non-isogenists.

If you don't care whether or not it is actually usable, then there's pqRSA which is essentially just regular RSA with (completely impractical) parameters that make it post-quantum secure.