BNO visa was issued on January 2021. That means around January or February 2025, some of the BNO HongKongers are going to apply for Indefinite Leave to Remains (ILR). If you check uk government website,  you must know the requirements. I summarize again here: 

• You can apply for settlement if you have a BNO visa and you’ve spent 5 continuous years in the UK..

• 2. Knowledge of language and life in the UK

In Fact, after the introductions of BNO visa, some of HK people have changed from existing UK visa to BNO visa. There are more cases now, you can see from facebook groups like Hong Kong BNO visa, etc, some of those changes from other UK visa to BNO visa have been rejected but offered 3 years of BNO visa again. You may think because they don’t use BNO visa for 5 years ? They don’t submit English test ? They don’t submit Life in the UK test ? They have criminal records in the UK ? Certainly not.