Is Guernsey included in standard UK or EU mobile roaming agreements for CoreESIM users with a domestic SIM?

Guernsey, while a British Crown Dependency, operates outside the UK's domestic mobile network and the European Union's 'Roam Like at Home' (RLAH) regulatory framework. Consequently, standard UK or EU mobile plans typically incur significant international roaming charges for data, calls, and SMS. CoreESIM strongly advises against relying on domestic SIMs for cost-effective connectivity in Guernsey, recommending a dedicated eSIM for predictable rates and optimal service.