Connecting to WiFi available on London Underground

Thank you Leelvan1
Sorry Martin, I do apologise, I didn't spot that the OP's original question regarded eSIM.
In case it's relevant to others on the thread, please could you confirm the settings for those with a physical sim?

No worries Donostio, I'll find out the situation for physical SIMs in the Underground network. I'll drop you an @ mention as soon as I have something for you.