Effective from December 28, 2021, the Hong Kong Immigration Department has implemented the "e-Visa". This means that applicants for entry visas, an extension of stay or changes to one's visa no longer will receive a paper sticker. Instead, newly approved permits will be delivered in a PDF format, also known as the "e-visa".
The practical application of the new standard means that new arrivals will have to present a printed version of the visa in A4 format or on a mobile screen.
Find F&Q and more information here (Hong Kong Immigration Department).