Is it still possible to apply for a BNO passport under the new rules in Hong Kong, or has the process been officially closed due to COVID-19 travel restrictions?
It is still possible to apply for a British National Overseas (BNO) passport from Hong Kong ¹. The UK government introduced the Hong Kong British National (Overseas) (BN(O)) route to provide the opportunity for BN(O) status holders and certain family members to live, work, and study in the UK ². Individuals can download a guide to learn more about how to apply for a BNO passport from Hong Kong ¹.
https://www.gov.uk/government/publications/how-to-apply-for-a-british-national-overseas-passport-from-hong-kong

