Doom Patrol was an American television series initially produced for the DC Universe streaming service, and later Max. Based on the superhero team of the same name, the series was created by Jeremy Carver. It began in 2019 and ended in 2023.
This world, and the characters that live in it, made a cameo appearance in the Arrowverse crossover event Crisis on Infinite Earths, according to which Doom Patrol takes place on Earth-21.
This cameo also confirms that Doom Patrol, while it may have been before, is no longer a part of the Titans continuity, as that same crossover confirms that series to be set on Earth-9, a similar but altogether different world.