The modem supports it just fine, but the carriers all block phones that aren't on their "approved" list (i.e., phones that they sell). I took a trip to the US e

The modem supports it just fine, but the carriers all block phones that aren't on their "approved" list (i.e., phones that they sell). I took a trip to the US earlier this year with my European Motorola G9 Plus. My Belgian sim roamed onto T-Mobile's network just fine but charged €13/MB; a T-Mobile SIM next to it worked fine for about 2 hours and then refused to connect ever again. This resulted in a delightful conversation with a support agent who told me without any sense of confusion that my phone physically did not have the hardware necessary to connect to T-Mobile's network while looking at my screen which read "Mobile Vikings - Roaming (T-Mobile)". AT&T wouldn't connect either; I ended up just going without for two weeks.