> 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.

If we're going on anecdotes, I've had a number of times when a physical SIM popped into a smartphone started behaving bewilderingly.

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?

> How do they know it's you

You scan the QR code and then download. Sometimes there is like a code you have to enter. It's a prepaid SIM, the carriers--particularly in East Asia or Africa--aren't particularly concerned with authenticating that much.