Is a SIM card needed for a remote hard reset through findmymobile.samsung?
The screen of a Samsung phone is broken completely and I want to take it to a repair shop, but before that I prefer to erase all data on it.
I have been able to verify that the phone was not associated to https://www.google.com/android/find?u=0 but that it was associated with https://findmymobile.samsung.com/#dialog . There, I can select the "Erase" option.
But the phone is marked as offline.
It has no SIM installed now but is powered on and vibrates from time to time like when emails and other messages are received. So, I thought it must be connected to the home wifi. Scanning on Linux with Wifi Guard, I can see one supplementary device connected that must be this phone, but it is still reported as offline on that site.
Should I insert a SIM for the remote erase procedure to work? Or would a wifi connection suffice? - in which case I'm wrong saying it is already connected to wifi etc.
The answer seems to be "yes". The phone can connect to the home wifi but that is not enough.
After using a SIM card - namely a different one than the one initially used on this phone (and listed on the Samsung site)
the new number was seen by the Samsung website,
the "Erase" option triggered a new message saying that the phone has to be unlocked first
remote unlock didn't work though: "Can't unlock your phone. It's not connected to a network."
That seems a vicious circle but the answer is nevertheless "yes": because a phone needs a cellular connection for the "remote erase" procedure to work, a SIM card is indeed needed, although that is not sufficient; the phone has also to be unlocked for it to receive/use the cellular signal etc.
It seems extremely difficult if not impossible to erase remotely a lost phone if it's disconnected. Luckily I have access to the phone, and can use the other old SIM and the biometric data to unlock it, and once I do that I'll update this answer.