I have a fun one: my iPhone (12 Pro) refuses to acknowledge that it has eSIM functionality, even though the hardware exists.

I'm fairly sure I know what the problem is! It was restored from a backup taken on an iPhone X that had two physical SIM slots (Chinese version). The new phone now seems to think it has two physical SIM slots: it shows an IMEI2 in About, but any attempt to use the eSIM functionality just fails (scanning a code does "nothing"; no "add" button is visible, etc.).

If this was an Android phone, I'd root it and just fix the offending network configuration file. I believe it's possible to tamper with a backup of the phone to fix the issue, but this would mean a full backup+restore cycle and some specialized tooling to go mucking with the backup.

I filed a Radar on it ages ago, but I'm assuming nobody ever picked it up.