I have always wondered how much Norse culture followed the Norsemen who settled in West Francia under Rollo in the Viking age. Obviously, by 1066 the area was Christian but there are also longships on the Bayeux tapestry.
Hopefully, there is a specialist around. I am a bit lost for where to start reading and I would prefer to start with reliable sources.
Lastly, if there is a Norse specialist around, I would also be interested if you knew the answer to a previous question I posted:https://www.reddit.com/r/AskHistorians/comments/6qrczf/how_frequently_were_holmgang_fought_or_invoked_in/
It's a very good question but not one that the French appear to be keen to find out about.
A recent genetic study in Brittany, using DNA samples drew criticism from the 'Mouvement Contre le Racism' as they feared that it would create racial antagonism between the 'True French' and those with ancestors from elsewhere.
The Professor of Medieval History in Caen spoke out against the study carried out by a UK University.
There's a dearth of archaeological evidence and continental records of the time were not well kept. The best records of the Norse in West Francia can be found in the Anglo Saxon Chronicle but they are rather perfunctory.
Many argue that Brittany would not have become so autonomous without the influence of the Norsemen but there is little to suggest that any social customs or institutions were changed by their arrival.