Zone information for United Kingdom will now return the following possible constituent countries for the UK:
Northern Ireland, Code:
British Forces, Code:
Merchants use provinces in their shipping zones settings to specify the rates for a country or province.
All existing shops that have United Kingdom in a zone will automatically include all UK constituent countries.
This data can be queried from the GraphQL admin api or REST admin api
Shipping/billing addresses in the UK are not supposed to contain these consitituent countries. To ensure that the shipping/billing address is displayed correctly, ensure you are using the format_address liquid filter to format correctly based on the address locale.