> How does that work with an eSIM?

Same, except you download it.

Ha, you say that.

When my wife’s German T-Mobile eSIM vanished during transfer to a new phone, their portal for downloading a new one required a token sent to that very phone number we just lost access to.

This meant we had to do a trip to their store where they said that there’s no process for the store to supply us with an eSIM, but they’ll setup a new traditional SIM which we could then convert to eSIM. Ridiculous! At least it was all free - apart from the time spent.

That was a few years ago, though. So, I very much hope they’ve improved on the process.

How do they know it's you, what makes you able to download the subscription token onto your device but not me? Do you need to receive a letter, or email via WiFi somewhere? Do mobile carriers accept unauthenticated devices to let them download SIMs, or does it require WiFi always?