“Do you know of any hard evidence that Leif Ericsson was Christian, or is it mostly anecdotal?”
I do not. Only read it a few times.
On another note, I watched a three episode program from the UK, about the Celts. It follows a premise that they made up a greater contribution to culture, language, even Christianity, than the lack of written record suggests.
They cited the Catholic church. They said when visitors came in the 500-700 period, they were amazed how advanced the church was.
There is a book titled “How the Irish Saved Civilization,” along a similar line.
Not every civilization was great about recording their history and some of the doers did more than the writers.