These television series follow the events of the original theatrical film, so they can be considered sequels of it, or take place before the events of the original theatrical film and are set within the same universe.
takes place approximately two decades after the events of Leroy & Stitch per Lilo's appearance as an adult with a daughter who looks identical to her as a child in a third-season episode.
Stitch & Ai takes place in 2016 at the latest per a calendar appearing in the episode "Dragon Parade".
How many years have passed since Leroy & Stitch is not specified, however, although Captain Gantu appears as part of the Galactic Council again after being reinstated to his post in Leroy & Stitch (he was forcibly retired from his post in Lilo & Stitch), and Cobra Bubbles appears without looking any different from his previous appearance in the Lilo & Stitch: The Series episode "Shush".
These television series are adaptations of the original theatrical film, but are neither prequels nor sequels: