After activating your eSIM via QR code or manual activation code, you may see the following error message:
Unsupported eSIM
"This eSIM is from a carrier that is not currently supported on this iPhone."
This error indicates that your device is locked by your carrier, and is not allowed to install plans from other carriers.
You can verify if your device is locked by following the steps below:
Go to Settings > General, and tap About
Under Carrier Lock, you should see the message: No SIM restrictions
If the Carrier Lock field says something different, the device is locked.
Solutions
Please contact your carrier to have your device unlocked. It can usually be done over-the-air by contacting the carrier's Customer Service phone number or live chat.