Disney+ looks like one worldwide service and is really several. In the United States it bundles Hulu's catalogue; in Europe, Latin America and much of Asia-Pacific the same subscription carries Star, a general-entertainment brand with a different library; and the sports, local productions and licensed films vary from country to country. A series available in the UK can be missing in Canada, and the Hulu titles never leave the US app.
Which version you see is decided by the country of your connection and, for some things, by the country of your account. A VPN changes the first: connect to a US server and the US app with its Hulu library loads; connect to London and you get the UK library with Star.
Disney does check for VPNs, mostly by address reputation. The symptom is error 73, which says the service is not available in your region even when you are connected to a supported country, or error 83 on devices the service decides it cannot trust. The address is what triggers it; a different server resolves it.
GhostShield covers the US in four cities, the UK, Canada and Australia, the four Disney+ libraries people ask about most.