In the settings app there is no reference to 'roaming' at all.  In most references to this online, the instruction is to open the settings app, choose 'Mobile Data' and then options shown include roaming.  In my settings app, the top level choice is 'Mobile' and when I choose this there are no references at all to 'roaming'.

My objective is to avoid roaming charges when overseas by using wifi calling exclusively - offline if not connected via wifi.

I am using a standard SIM.  I used ESIM for a while but with the nearest 2D store an hour's drive away, it is difficult to swap to a backup (android) phone that I have if the need arises.