A sample of some recent articles
"China Is Forcing Its Biggest Cantonese-Speaking Region To Speak Mandarin" https://www.businessinsider.com/china-is-forcing-its-biggest...
"Hong Kong education chief forced to clarify controversial comments about teaching Chinese language in Cantonese" https://amp.scmp.com/news/hong-kong/education/article/216738...
"Guangzhou Television Cantonese controversy" https://en.wikipedia.org/wiki/Guangzhou_Television_Cantonese...
And there's also evidence of the CCP re-writing history https://www.nytimes.com/2017/05/05/opinion/ching-cheong-hong...
You've also ignored the point about how HK did not succumb to the Cultural Revolution. I think that this is an important point on the timeline where the culture of HK diverged from the remaining Guangdong region, which is one of the things that give Hongkongese their unique Chinese identity. For example, Hongkongese retained their religious freedom, as well as freedom of the arts, and language.