I’m in sword and shield and want to breed for a shiny Rowlet in a luxury ball. Is there any way to get a Rowlet in a luxury ball, or is it still impossible without hacking?
Unfortunately, you cannot.
Now, this makes it seem possible. However, the female species can only breed to make its own species, so technically, if you don't hack in a rowlet with a luxury ball, then you can't get it.