Anyway, a show's canon is an official story line that is maintained throughout the existence of that show. A canon is maintained by way of continuity from one episode to the next or one series to the next.
There is a canon connecting What's New, Scooby-Doo? to A Pup Named Scooby-Doo as revealed in the WNSD episode A Terrifying Round with a Menacing Metallic Clown. That episode features a flashback to A Pup Named Scooby-Doo.1
However, there is no canon for the entire Scooby universe.
The Scooby story line was radically altered with the live-action movie Scooby-Doo! The Mystery Begins (2009), with the animated series Scooby-Doo! Mystery Incorporated (2010) and with the 2018 film Daphne & Velma.
On the other hand, the Scooby universe has featured several cannons, such as the one in the direct-to-video Big Top Scooby-Doo! (2012).
Information Source:
1A Terrifying Round with a Menacing Metallic Clown. What's New, Scooby-Doo? https://www.watchcartoononline.com/whats-new-scooby-doo-episode-36-a-terrifying-round-with-a-menacing-metallic-clown