[chvid]

Last that I was in China I used my standard Danish phone subscription from 3. Fast, flat rate data and full access to Google etc. in mainland China.

https://www.3.dk/abonnementer/fordele/3likehome/

[pmlnr]

This is orthogonal. Yes, my UK giffgaff worked, but UK - or Hungarian - phone numbers are not accepted by the Alipay app for registration.

[chvid]

Sure. I still couldn't do KYC in China and get an wechat wallet but global mobile roaming and internet connectivity is a first step ...