I activated a Thai SIM (True) inside of Europe before traveling no problem, so it's not a technical limitation. I think brands like Saily that specifically target travelers are also activated beforehand, so when you arrive you immediately have data.

True, both networks I have in Europe don't allow it. It's one of the reasons I don't like eSIM, there are a lot more restrictions than with real SIMs. With those I can simply pull one of my cards out of my phone and put it in my tablet or 4G modem for an hour while travelling. With eSIM I have to unregister it and get a new QR every time, registering it doesn't work abroad, and they can deny activation based on the device.

> Is that even a ban? I didn’t think eSIM activation typically roams — I thought it only worked on home networks.

While I was in the US, I swapped iPhones and successfully activated both NTT docomo and Au (KDDI) eSIMs while roaming. It definitely works when you're out of home network.

Mysterious - I have downloaded UK eSIMs over WiFi, and then activated/connected as if I were roaming, from other parts of Europe.