According to an article on AllAfrica, the National Bank of Angola introduced a new polymer 500-kwanza note (B558a) on 17 September 2020. This joins the new 200-kwanza note (B557a) introduced on 30 July 2020, and will be followed by a new 1,000-kwanza note (B559a) in October and 2,000-kwanza note (B560a) in November.
Courtesy of Andrea Bossi.