In germany there may be problems with data protection when loading external content.
SwaggerUICSS, SwaggerUIBundle and SwaggerUIStandAlonePreset come from unpkg.com
Is there an approach to prevent this?
As you might have already noticed already, those three identifiers you mentioned are global variables in unit XData.SwaggerUI.Service.Internal. That's exactly the purpose of them being declared as such.
You can simply change their value, so that instead of coming from unpkg.com, you change their URL to be loaded from anywhere in your local network. Change their URLs, and then host them whenever you want, so they are not loaded as external content.