It's not just recent migration to Guangdong province. The eastern half of Guangdong is traditionally Hakka-speaking. Most Hakkas don't speak Cantonese, and that shouldn't be surprising.
I am confused by this comment. Are you talking about Chaozhou (潮州)? That city is on the border between Guangdong and Fujian (but lies in GD), but the locals are overwelming Canto speakers. There are many who have migrated to Hongkong over the last 75 years.
Isn't Chaozhou mostly Teochew-speaking? Wikipedia claims there are 10 million Teochew speakers in Chaozhou while listing the total population as 2.7 million, which obviously doesn't add up. https://en.wikipedia.org/wiki/Chaozhou#Language (My guess is metropolitan area vs. city boundaries.) But given that Teochew is named after Chaozhou (modulo romanization) I would've expected it to be locally dominant over Cantonese.
