Keeping an old phone as a spare is a very smart move. My 11 went on the fritz a couple of weeks ago the day of a flight to mainland. Local Apple tech said it had to go to mainland for two weeks for servicing. I swapped SIM to my previous phone (6, I don't update frequently ) and was off and running. UA app works on 6 and all my data showed up, and, for some reason I don't understand, probably a hundred contacts I didn't recognize. Handy for return because quarantine officials want to check the number you give them on arrival back to Hawaii.

I've never felt as lost as when my phone went inoperative. It's like a vital organ nowadays