Nomad

Most Nomad eSIMs are data only, with no phone number: you cannot make calls or send or receive SMS, so codes go to your home SIM, which should stay your default voice and SMS line. A plan does not start when you install it. It activates when the eSIM connects to a local network at the destination with data roaming on, and Nomad starts it automatically on the 60th day after purchase if it has not activated by then. Add-on data activates by itself once the base plan's data is used up or the plan expires. Nomad's help center says add-on purchases are restricted in China, the UAE and India and that new China plans cannot be bought there, so buy enough before you arrive. Nomad lists country plans on Verizon and AT&T in the US, KDDI au and SoftBank in Japan, CMCC HK, csl and 1O1O in Hong Kong, Chunghwa and Taiwan Mobile in Taiwan, and China Unicom and China Telecom in China.