"Remove This Device" on iCloud gives
"Cannot Remove iPhone. Prepare It for Repair or Trade In?
This iPhone is linked to your Apple Account and cannot be removed while it is online, but you can still prepare it for repair or trade in."
I turned off the iPhone for several minutes, and then was able to use Remove This Device; iCloud's going to keep a handle on it for 30 days.
I powered up the iPhone, and went to Stolen Device Protection, to turn it off. It tried twice on FaceId, then asked for the iPhone passcode. It accepted the code, and showed SDP as Off.
FaceID still doesn't work for login. I rebooted, and still not working for login or for apps.
I reset FaceId, and started 'Set Up Face Id'. The camera gets to 'Position your face in the frame', fails over to 'Reposition your face in the frame, your face is out of view', and sits there. Restarting the phone doesn't help with that.
So, I'll go look for a thread about resetting FaceId, but at least I've turned off Stolen Device Protection, for which I thank you.