The Cornish are English, like the Devonians, the Men of Kent etc.
Please don’t refer to them as if they were some backward tribe of aboriginals who Henry exterminated. That would be a bizarre mistake, a distortion of history with identity politics.
Cornish Lords rose up in rebellion on at least two occasions, seeking the help of other Englishmen to fight the King. Unfortunately they lost - and Henry carried out savage reprisals - but they weren’t some different race of people that the English somehow need to make reparations to.
Not all history is about race. Not all history needs to echo the identity preoccupations of the American Left
The Cornish are Celtic in origin ~ they are not Sassanach!