You can now withdraw cash from an ATM with a mobile generated QR code.
Not sure if it works with a screenshot of a QR code on a phone.. i.e. if there is some sort of bi-directional exchange during the withdrawal or a static image scan.
Unfortunately looks like it is available at a limited set of banks - not sure what the commonality is in terms of ATM / IT suppliers or vendors.
https://www.jetco.com.hk/en/atm/cardless-withdrawalBank of Communications (Hong Kong) Limited
The Bank of East Asia, Limited
China CITIC Bank International Limited
China Construction Bank (Asia) Corporation Limited
China Merchants Bank Hong Kong Branch
Chong Hing Bank Limited
Citibank (Hong Kong) Limited
Dah Sing Bank, Limited
Industrial and Commercial Bank of China (Asia) Limited
Public Bank (Hong Kong) Limited
Shanghai Commercial Bank (Hong Kong) Limited