From the horse's mouth:

https://www.info.gov.hk/gia/general/...2042200621.htm

Arrival test:
RAT and PCR tests are sampled at the airport upon arrival. If RAT -ve then head to the hotel instead of wait for result at the airport.

Entry status:
A visitor who holds visa on arrival travel documents would be permitted to enter

Flight Ban Mechanism triggers five days (OR):
5 positive
5 % of passengers tested positive
3 positive plus ONE improperly documented passenger.