Porting a program to Quantii can be fairly involved. If it's a command line program, it can run on Quantii by being ported to LLVM's wasm32-wasi target. For GUI programs, your GUI toolkit must either support the Daku API or you can opt to re-write the graphical portion using the provided API.
Quantii doesn't currently support threading in WASM due to limitations of the Rust compiler (not being able to spawn a thread). This means each thread must become a Daku asynchronous task. Tasks can only communicate over Daku channels, so mutexes and non-locking data structures must be replaced.