Paternal line (on paper) not lining up with Y-DNA

[Sanderson69]

Hello there.
My dad did a DNA test and found that his Y-DNA was under the haplogroup of R-L21 and the subclade R-DF13, which is very much distinctive to the western, isolated parts of the British Isles (as well as Brittany), and thus amongst the Irish, Welsh & Western Scottish. However, we traced back on our family tree our paternal line to Suffolk in the early 19th Century, where Anglo-Saxon Y-DNA prevails and where this haplogroup is incredibly rare. Anyone else have this haplogroup but not from western areas such as Northern Ireland?

 

[Robotnick]

A lot of L21 survived in Anglo-Saxon areas. It Pervades most of Britain from what I understand, even if there is much in the way of Germanic Y lineages in Eastern Britain.
There were even male Britons who integrated with Anglo-Saxon society and religion, as evidenced by recent archaeology and genetics (e.g. a 100% autosomally Briton man being buried in a Germanic heathen style grave)

The Anglo-Saxon migration did not "replace" the Britons in Eastern Britain, but largely comingled with them over time.

 

[Riverman]

Hello there.
My dad did a DNA test and found that his Y-DNA was under the haplogroup of R-L21 and the subclade R-DF13, which is very much distinctive to the western, isolated parts of the British Isles (as well as Brittany), and thus amongst the Irish, Welsh & Western Scottish. However, we traced back on our family tree our paternal line to Suffolk in the early 19th Century, where Anglo-Saxon Y-DNA prevails and where this haplogroup is incredibly rare. Anyone else have this haplogroup but not from western areas such as Northern Ireland?

R-DF13 is common throughout Europe, especially in the West, not just Ireland, where it's just most common. Compare:
https://discover.familytreedna.com/y-dna/R-DF13/frequency

He should do a Big Y/WGS test to determine his exact subclade or look for close STR-matches. That's more conclusive than a haplogroup which is 4.500 years old and spread in many parts of Europe.