Unable to answer "What’s the surface of the sidewalk here?" – Trafalgar Street (Minor/Unclassified Road) – https://osm.org/way/393283522 via StreetComplete_ee 57.0:

Has both bricks and asphalt. See photo.

Attached photo(s):
https://westnordost.de/p/201986.jpg
https://westnordost.de/p/201987.jpg
https://westnordost.de/p/201988.jpg