"Do you have a new keyboard?"
Translation:Oes bysellfwrdd newydd gyda chi?
I got ‘Oes gennych chi fysellfwrdd newydd?’ (I did that and it said it was ‘almost correct’ because I wrote ‘b’ instead.)
Why the initially mutation?
The 'technical' rule at work here is that "Bysellfwrdd" in this sentence is the object of the verb (In this case "Oes") though an easier way of mutating right in this situation is just to mutate any time after a pronoun.