Joker is a DC movie, but it’s not connected to the DCEU. The movie is set in 1981, following the criminal descent of failed stand-up comedian Arthur Fleck. Robert De Niro, Zazie Beetz, Frances Conroy, Brett Cullen, and Marc Maron co-star.
Article source: https://www.cinemablend.com/news/2478974/joker-has-screened-early-reactions-say-joaquin-phoenix-deserves-oscar-for-this-masterpiece