"She can't drive."
Translation:Dyw hi ddim yn gallu gyrru.
Isn't "dyw" the northern variation of "ydy"? Could I say "Ydy hi ddim yn gallu gyrru."?
I think you're thinking of "yw", without the negative d- at the beginning (Athro yw fy mrawd, my brother is a teacher, etc.).
And "Dydy hi ddim yn gallu gyrru." as far as I know.
I didn't know the "d" made it negative. But would that mean "dyw/yw" is northern and "dydy/ydy" is southern? I want to focus on southern dialects.
Both are used all over Wales, and even if one was used more in some dialects that others, you will come across both in any reading, listening or watching TV that you do.
Best to learn as many word-forms and pattern variations as you can, really. When it comes to speaking you can concentrate on using a consistent accent. Accents are the main variations across the 4-6 main dialects in Wales. The computer-generated Duo voice is a neutral accent which should be understandable by anybody. As and when you use Welsh face-to-face you could start to adapt that pronunciation if you wished.
Duo only really highlights a very few dialect variations in any case, a 'standard' Welsh and then a few variants from north or north-west Wales. Nothing specific from mid-Wales, for example, or from Pembroke/Ceredigion, or Gwent/Glamorgan, ...