HONG KONG—Two Hong Kong pro-democracy activists pleaded guilty on Tuesday to charges related to an illegal assembly during mass anti-government protests in August 2019, while seven others, including media tycoon Jimmy Lai, pleaded not guilty. The 2019 protests, fuelled by fear among locals that communist Beijing was curbing the wide-ranging freedoms promised to the former British colony upon its return to mainland rule in 1997, plunged the semi-autonomous city into its biggest crisis since the handover. The rally in August 2019 was estimated to have drawn more than 1 million people, despite heavy rain, and provided a respite from the clashes between protesters and police seen often at demonstrations in the months before and after. Former pro-democracy politician and activist Au Nok-hin pleaded guilty to organising and knowingly taking part in an unauthorised assembly, while Leung Yiu-chung, another activist, pleaded guilty to participating in an illegal assembly. Leung and Au …