This is super neat - SBCL is an awesome language implementation, and I've always wanted to do CL development for a "real" game console.
I'm also surprised (in a good way) that Shinmera is working on this - I've seen him a few times before on #lispgames and in the Lisp Discord, and I didn't know that he was into this kind of low-level development. I've looked at the guts of SBCL briefly and was frightened away, so kudos to him.
I wonder if SBCL (+ threading/SDL2) works on the Raspberry Pi now...