Consequence of applying Use & Enjoyment rules on roaming services: third-country (non-EU) operators will have to register for VAT in all those member states whenever customers use roaming services there, regardless of the amount at stake. Compliance costs could rise significantly, as operators are forced to juggle different taxes.
Source International Tax Review
See also ECJ C-593/19 (SK Telecom) – Roaming services, effective use and enjoyment, VAT refund