Hello! same problem (iphone xr to 12) but I didn't succeed. I talked to the people from support (apple) for almost 2 hours, and I tried the following solution that they proposed. Connect Mac or PC (itunes) and downgrade.(https://support.apple.com/en-us/HT203282) But know that it didn't work that way for me either (I tried 3 times) and I'm still stuck on iOS 17. I'll will try not to transfer, just connect to the iCloud account on the new phone and to access the last backup from version 16.6.
lucamara
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