Cannot have both eSIM and Physical SIM in same device

• iPhone 16 Pro
• iOS 18.2

While physical SIM is installed in the device, neither eSIM and SIM are enabled.

• Physical SIM is "Taiwan"
• eSIM is "Australia"

Step 1: Both installed.

• Mobile ("Cellular" in en-US) is Off
• No service

However, both Lines are appearing in the list when I navigate into Mobile:

Each Line is enabled in it's settings panel

Step 2: Eject physical SIM and see what happens

• Service is available

Step 3: Test Physical SIM in a known working device.

• In this case, the test device is an iPhone 11, iOS 18.1.1
• Taiwan SIM has service

Step 4: Plug physical SIM back into iPhone 16

• Still looks ok

Step 5: Reboot iPhone

• Unfortunately, the configuration does not survive the reboot. The state is back to step 1, no service.

I haven't tried un-installing the eSIM as it's a hassle and I don't think it will help us understand anything.

TIA