There is a sentence in this unit which says "The dice are under the sofa" which expects a translation of Mae'r dis o dan y soffa.
I can't comment there since there aren't any comments yet and apparently I'm unable to open a new sentence discussion in the new website.
As I understand it, dis is only one die/dice and disiau is multiple dice -- so either the English sentence should be changed to "This dice is" or it should reject mae'r dis and expect/accept mae'r disiau instead.
It is the most commonly used term in US and Canadian English. Telly should certainly also be accepted, so you should report it, if you haven't. In my experience, the various courses usually start out with mostly either British or American standard, but then come to accept the other translations as people report them.
I suppose I assume that the Welsh course starts off with mainly British English because of the close connection between England and Wales, but fair enough, I didn't register what you had said but we certainly don't use 'TV' in England. I did report it but am told Duo stick to TV and television, neither of which I would use conversationally.
I didn't see that answer until you pointed it out. I would have expected them to start from UK standards in translations as well. Most of the other language teams clearly strive to accept translations in all regional Englishes, even though that can be really difficult in the education lesson, for instance.