I'm following TheLortex's notes on how to run my unikernel on esp32, in particular odroid-go. (Thanks to @julow and @clecat for the pointers and help.)
First attempt to install the cross-compiler for esp-32:
opam repo add git https://github.com/well-typed-lightbulbs/opam-cross-esp32.git
opam install mirage-esp32 ocaml-esp32.4.07.1
which is supposed to work for linux. On mac, I get the error