I remembered a while ago you meed to first get an physical SIM to activate the line then switch to eSIM. Now sure about now. I’m currently with Google Fi on an eSIM in my 12 mini.
I just set up my iPhone with a Fi eSIM without having to get a physical SIM first. There are oblique references on how to do it at checkout that involve backing out of the default flow and then choosing your iPhone model from a compatibility list. It was quite the maze.