I know Google is actively working on the Cantonese version of Google Assistant, though not sure when it'll be officially released.
Source: I'm a native speaker of one and fully fluent in the other.
and if written Cantonese is mostly informal (conversation, shop signs) it will not often be multilingual. so the approach that has worked for most languages wouldn't work then.
and it surely wouldn't work for a completely different, lossy orthography - without independent training.