I dont know how well known this is, or even if it applies everywhere, but where I live (Norway) the new iPhones esim arent supported by any carriers yet. What people are reporting to work however, is having the carrier send them an esim (qr code) for the Samsung galaxy watch (or what ever it is called) which works just fine. You will get a warning saying the carrier isnt supported and that this may cause decreased batterylife, but it works.