Thanks for linking this. I was interested in how it worked but I didn't know enough elixir to get around the codebase by myself. This entry point is very informative for how they managed to do it.

I just looked at the macOS part, but the tl;dr for that is they seem to have compiled the elixir program into a binary and wrote enough swift to manage the lifecycle of the elixir program and signed it and notarized it and prepared it for shipment using CLI via shell! invocations. I didn't look at the windows way of doing things but I imagine it's similar.