For whatever it's worth, the one resource I recall for DS homebrew dev with Rust is https://github.com/SeleDreams/libnds-rs , but it hasn't been maintained in a while.
I did see that but the readme kind of scared me off.
Can you make a full fledge game on it?
With enough effort yeah. Since it can use all of libnds all of the input, displays, memory regions are available to use.