"Demo totalmente nueva. ¡Descárgala gratis!" is what you can read under the Hyrule Warriors: Age of Calamity icon on the Spanish Nintendo Switch eShop. In Spanish, it means "totally new demo, download it for free!"
Nintendo has not announced a demo version of the upcoming musou game, but it seems all but confirmed right now. Following a leak from Nintendo Korea, Revogamers captured that small line from the official store. By clicking on it you are not sent to a page with a link to download the demo, though, just to the regular game page to pre-order it.
We may have to wait a little bit longer before Hyrule Warriors: Age of Calamity demo version is available. The Team Ninja developed game is coming out on November 20.