Hi! Welcome!!
What a gorgeous kitty!
I see some underlying stripes - I don't know for certain, but I'm not sure that those appear in a Korat or Russian blue, but your furbaby is a truly beautiful cat, no doubt
I would describe your beautiful new family member as a blue domestic shorthair. The solid blue color is common in the domestic cat population and doesn't indicate Russian Blue or Korat ancestry. Most cats aren't any particular breed.
He’s so handsome! I would describe him as a blue Domestic Shorthair. You could also call him a Maltese cat. I think, that due to his triangular head and big ears, Russian Blue would be the closest breed lookalike.