I'm using international roaming in Europe. In France it worked good. In Czech Republic it is incredibly fiddly.
At first, I had trouble getting data working. Fixed that with some help from the good doctor.
Sometimes I still have to go into settings and choose the network operator to get data started, but at least it works.
Then it started doing this thing where I get data but the network doesn't recognize my telephone -- it shows "Emergency Calls Only"
Spent lots of time messing with settings trying to get connected.
Finally, I tried turning off roaming and data, and then going into settings and choosing the network operator. Now the phone is on.
Makes me wonder what'll go wrong next, and what contortions I'll have to go through to find a fix.
Marking this as a question, in case somebody has a comment.