Foreign nationals who require visas for Hong Kong (if they cannot enter visa-free of charge, want to stay for lengthier than permitted by their visa exemption, or want to work, analyze or create/sign up for a company) can either apply for a single in a Chinese embassy or consulate, https://www.aljazeera.com/news/2020/07/pro-democracy-activists-books-removed-hong-kong-libraries-200705135114481.html