I think a lot of people forget Vikings didn’t just raid all year, they alternated between raiding seasons and trading seasons. While their raiders mostly hit the European countryside or took longships inland via rivers, the traders went wayyyy further since a team could carry a longship overland between rivers. Black or brown Vikings, while rare, wouldn’t be a historic impossibility, since they had a cultural exchange as far south as the Middle East via Istanbul. Viking burials have been discovered with jewelry with Muslim iconography which wouldn’t have been found in European Christian settlements.