Just an update, I ordered the proper US modem from Purism, it took less than two weeks to get it (unlike the phone itself), phone works fine in calls and SMS (didn’t test MMS yet). Also didn’t need to do anything other than physically install it which wasn’t bad. Didn’t have to go on the command line and update anything to recognize a change in hardware, it works as long as you swap it out. So if I ever go to Europe again, I may swap out modems since now I have a US and European modem for this device.