> SIM-free phone
Is the modem completely disabled? Does it still show the "SOS" option that allows you to call 911 without a SIM? If so, and if it's ever been turned on in your residence, there's a decent chance the IMEI could be traced back to your house just based on pattern-of-life movement.
That's why you also need to enable airplane mode.
Which you can just engage on your current phone.
Airplane mode often leaves bluetooth on, with all the tracking that enables.
On Android at least for now, you can use systemui tuner to pick what gets toggled for airplane mode: Cell, Bluetooth, Wi-Fi, NFC, WiMAX.
No root needed