Update. I had to rewire stuff to fit everything but now it's all connected(except for gain). Still haven't programmer and tested it but that will come next.
In the mean time, I tried to get Lua running but that's not exactly straightforward for Rust on esp32. I don't think anyone has done it yet and the existing libraries only really target x86 and wasm. But there exist a C++ IDF Lua module and WIP Rust Lua interpreter, which gives a couple of options:
>get that interpreter running on esp (currently it causes stack overflow for some reason, even at 32k stack. some corruption maybe?)
>get lua-src to compile Lua on xtensa, trying to imitate that IDF Lua, so mlua library can work
>try to integrate IDF Lua module directly into the project and write my own bindings/wrapper
Every option requires some non-trivial work and neither is guaranteed to work. However the first one would probably be the nicest since it would give us full control over the interpreter. We could emulate Pico-8 fixed point precision and whatever other wacky idea they had. But I have no idea how stable and usable this project is. The author still seems to be actively working on it so I could try contacting him. Alternatively second option, if it works, it would give us really nice, battle-tested bindings, since mlua is quite popular library.
3rd option would probably take most work and would suck so better save it for last.