@klauskobald,
CanvasJS is a client-side library that requires browser environment and APIs to run. You should prevent running CanvasJS in the server environment. To do so in Nuxt app, you can use .client
suffix to your component containing CanvasJS Chart. Please checkout this StackBlitz example for an example on integrating CanvasJS Charts in Nuxt app.
Also, check out this documentation page of nuxt to know more about client side component.
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Manoj Mohan
Team CanvasJS