Later in my visit to Belfast, I learned that this had been a Primark Store, but was badly damaged in a fire in August 2018. https://www.bbc.co.uk/news/uk-northern-ireland-45330801
White sheeting was draped across the top of the frontage (presumably as a protection from the elements) and the remains from the interior sticking up above it made me think of the Titanic sinking in the North Atlantic. Belfast is Titanic Town! Two hours and a few minutes.